feat: implement NIP-10 thread chat support

Add complete NIP-10 thread chat implementation enabling "chat nevent..." to
display kind 1 threaded conversations as chat interfaces.

**Type Definitions**:
- Add ThreadIdentifier for nevent/note event pointers
- Add "nip-10" to ChatProtocol type
- Extend ConversationMetadata with thread-specific fields (rootEventId,
  providedEventId, threadDepth, relays)

**NIP-10 Adapter** (src/lib/chat/adapters/nip-10-adapter.ts):
- parseIdentifier: Decode nevent/note format, reject non-kind-1 events
- resolveConversation: Fetch provided event, find root via NIP-10 refs,
  determine conversation relays (merge hints, outbox, fallbacks)
- loadMessages: Subscribe to kind 1 replies, kind 7 reactions, kind 9735 zaps
- sendMessage: Build proper NIP-10 tags (root/reply markers), add p-tags for
  all participants
- sendReaction: Send kind 7 with proper event/author references
- Smart relay selection: Merges seen relays, nevent hints, author outbox,
  user outbox (limit 7 relays for performance)

**ChatViewer Updates**:
- Detect NIP-10 threads (protocol === "nip-10")
- Fetch and display root event at top (centered with KindRenderer)
- Show visual separator ("Replies") between root and messages
- Update empty state message for threads ("No replies yet...")
- Enhanced header: Show "Author • Preview" for thread chats
- Update getAdapter to handle "nip-10" protocol

**Chat Parser**:
- Add Nip10Adapter to priority list (before other adapters to catch
  nevent/note)
- Update error message with nevent/note format examples
- Update adapter priority documentation

**Component Enhancements**:
- ReplyPreview: Show "thread root" when replying to root event (NIP-10)
- RelaysDropdown: Support conversation.metadata.relays for thread relay
  breakdown
- ChatMessageContextMenu: Add "Zap" option to context menu (opens ZapWindow)

**Features**:
- Root event displayed with full feed renderer (can interact: like, zap, etc.)
- All replies shown as chat messages with proper threading
- Reply/React/Zap options on all messages
- Relay dropdown shows breakdown of thread relays
- Participants dropdown shows all thread participants
- @ mention autocomplete works for participants
- Proper NIP-10 tag structure for nested replies
- Smart relay selection for maximum reach

**Usage**:
  chat nevent1qqsxyz...  # Thread with relay hints
  chat note1abc...       # Thread with event ID only

Root event is centered at top, all replies below as chat messages. Sending
replies creates kind 1 events with proper NIP-10 root/reply markers and
p-tags for all participants.

src/components/ChatViewer.tsx

@@ -24,6 +24,7 @@ import type {
 } from "@/types/chat";
 import { CHAT_KINDS } from "@/types/chat";
 // import { NipC7Adapter } from "@/lib/chat/adapters/nip-c7-adapter";  // Coming soon
+import { Nip10Adapter } from "@/lib/chat/adapters/nip-10-adapter";
 import { Nip29Adapter } from "@/lib/chat/adapters/nip-29-adapter";
 import { Nip53Adapter } from "@/lib/chat/adapters/nip-53-adapter";
 import type { ChatProtocolAdapter } from "@/lib/chat/adapters/base-adapter";
@@ -33,6 +34,7 @@ import { parseSlashCommand } from "@/lib/chat/slash-command-parser";
 import { UserName } from "./nostr/UserName";
 import { RichText } from "./nostr/RichText";
 import Timestamp from "./Timestamp";
+import { KindRenderer } from "./nostr/kinds";
 import { ReplyPreview } from "./chat/ReplyPreview";
 import { MembersDropdown } from "./chat/MembersDropdown";
 import { RelaysDropdown } from "./chat/RelaysDropdown";
@@ -507,6 +509,16 @@ export function ChatViewer({
       ? conversationResult.conversation
       : null;
 
+  // Check if this is a NIP-10 thread
+  const isThreadChat = protocol === "nip-10";
+
+  // Fetch root event for NIP-10 threads
+  const rootEventId = conversation?.metadata?.rootEventId;
+  const rootEvent = use$(
+    () => (rootEventId ? eventStore.event(rootEventId) : undefined),
+    [rootEventId],
+  );
+
   // Slash command search for action autocomplete
   // Context-aware: only shows relevant actions based on membership status
   const searchCommands = useCallback(
@@ -821,10 +833,23 @@ export function ChatViewer({
               <Tooltip open={tooltipOpen} onOpenChange={setTooltipOpen}>
                 <TooltipTrigger asChild>
                   <button
-                    className="text-sm font-semibold truncate cursor-help text-left"
+                    className="text-sm font-semibold truncate cursor-help text-left flex items-center gap-1.5"
                     onClick={() => setTooltipOpen(!tooltipOpen)}
                   >
-                    {customTitle || conversation.title}
+                    {isThreadChat && rootEvent ? (
+                      <>
+                        <UserName
+                          pubkey={rootEvent.pubkey}
+                          className="text-sm font-semibold flex-shrink-0"
+                        />
+                        <span className="text-muted-foreground">•</span>
+                        <span className="truncate">
+                          {customTitle || conversation.title}
+                        </span>
+                      </>
+                    ) : (
+                      customTitle || conversation.title
+                    )}
                   </button>
                 </TooltipTrigger>
                 <TooltipContent
@@ -936,69 +961,90 @@ export function ChatViewer({
       </div>
 
       {/* Message timeline with virtualization */}
-      <div className="flex-1 overflow-hidden">
-        {messagesWithMarkers && messagesWithMarkers.length > 0 ? (
-          <Virtuoso
-            ref={virtuosoRef}
-            data={messagesWithMarkers}
-            initialTopMostItemIndex={messagesWithMarkers.length - 1}
-            followOutput="smooth"
-            alignToBottom
-            components={{
-              Header: () =>
-                hasMore && conversationResult.status === "success" ? (
-                  <div className="flex justify-center py-2">
-                    <Button
-                      onClick={handleLoadOlder}
-                      disabled={isLoadingOlder}
-                      variant="ghost"
-                      size="sm"
-                    >
-                      {isLoadingOlder ? (
-                        <>
-                          <Loader2 className="size-3 animate-spin" />
-                          <span className="text-xs">Loading...</span>
-                        </>
-                      ) : (
-                        "Load older messages"
-                      )}
-                    </Button>
-                  </div>
-                ) : null,
-              Footer: () => <div className="h-1" />,
-            }}
-            itemContent={(_index, item) => {
-              if (item.type === "day-marker") {
-                return (
-                  <div
-                    className="flex justify-center py-2"
-                    key={`marker-${item.timestamp}`}
-                  >
-                    <Label className="text-[10px] text-muted-foreground">
-                      {item.data}
-                    </Label>
-                  </div>
-                );
-              }
-              return (
-                <MessageItem
-                  key={item.data.id}
-                  message={item.data}
-                  adapter={adapter}
-                  conversation={conversation}
-                  onReply={handleReply}
-                  canReply={canSign}
-                  onScrollToMessage={handleScrollToMessage}
-                />
-              );
-            }}
-            style={{ height: "100%" }}
-          />
-        ) : (
-          <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
-            No messages yet. Start the conversation!
+      <div className="flex-1 overflow-hidden flex flex-col">
+        {/* NIP-10 Thread: Show root event at top */}
+        {isThreadChat && rootEvent && (
+          <div className="border-b bg-muted/10 flex-shrink-0">
+            <div className="max-w-2xl mx-auto py-4 px-3">
+              {/* Use KindRenderer to render root with full feed functionality */}
+              <KindRenderer event={rootEvent} depth={0} />
+            </div>
+            {/* Visual separator */}
+            <div className="flex items-center gap-2 px-3 py-1 text-xs text-muted-foreground">
+              <div className="flex-1 h-px bg-border" />
+              <span>Replies</span>
+              <div className="flex-1 h-px bg-border" />
+            </div>
           </div>
         )}
+
+        {/* Scrollable messages list */}
+        <div className="flex-1 overflow-hidden">
+          {messagesWithMarkers && messagesWithMarkers.length > 0 ? (
+            <Virtuoso
+              ref={virtuosoRef}
+              data={messagesWithMarkers}
+              initialTopMostItemIndex={messagesWithMarkers.length - 1}
+              followOutput="smooth"
+              alignToBottom
+              components={{
+                Header: () =>
+                  hasMore && conversationResult.status === "success" ? (
+                    <div className="flex justify-center py-2">
+                      <Button
+                        onClick={handleLoadOlder}
+                        disabled={isLoadingOlder}
+                        variant="ghost"
+                        size="sm"
+                      >
+                        {isLoadingOlder ? (
+                          <>
+                            <Loader2 className="size-3 animate-spin" />
+                            <span className="text-xs">Loading...</span>
+                          </>
+                        ) : (
+                          "Load older messages"
+                        )}
+                      </Button>
+                    </div>
+                  ) : null,
+                Footer: () => <div className="h-1" />,
+              }}
+              itemContent={(_index, item) => {
+                if (item.type === "day-marker") {
+                  return (
+                    <div
+                      className="flex justify-center py-2"
+                      key={`marker-${item.timestamp}`}
+                    >
+                      <Label className="text-[10px] text-muted-foreground">
+                        {item.data}
+                      </Label>
+                    </div>
+                  );
+                }
+                return (
+                  <MessageItem
+                    key={item.data.id}
+                    message={item.data}
+                    adapter={adapter}
+                    conversation={conversation}
+                    onReply={handleReply}
+                    canReply={canSign}
+                    onScrollToMessage={handleScrollToMessage}
+                  />
+                );
+              }}
+              style={{ height: "100%" }}
+            />
+          ) : (
+            <div className="flex h-full items-center justify-center text-sm text-muted-foreground">
+              {isThreadChat
+                ? "No replies yet. Start the conversation!"
+                : "No messages yet. Start the conversation!"}
+            </div>
+          )}
+        </div>
       </div>
 
       {/* Message composer - only show if user can sign */}
@@ -1070,11 +1116,13 @@ export function ChatViewer({
 
 /**
  * Get the appropriate adapter for a protocol
- * Currently NIP-29 (relay-based groups) and NIP-53 (live activity chat) are supported
+ * Currently NIP-10 (thread chat), NIP-29 (relay-based groups) and NIP-53 (live activity chat) are supported
  * Other protocols will be enabled in future phases
  */
 function getAdapter(protocol: ChatProtocol): ChatProtocolAdapter {
   switch (protocol) {
+    case "nip-10":
+      return new Nip10Adapter();
     // case "nip-c7":  // Phase 1 - Simple chat (coming soon)
     //   return new NipC7Adapter();
     case "nip-29":

src/components/chat/ChatMessageContextMenu.tsx

@@ -133,6 +133,18 @@ export function ChatMessageContextMenu({
     setEmojiPickerOpen(true);
   };
 
+  const openZapWindow = () => {
+    if (!zapConfig || !zapConfig.supported) return;
+
+    addWindow("zap", {
+      recipientPubkey: zapConfig.recipientPubkey,
+      eventPointer: zapConfig.eventPointer,
+      addressPointer: zapConfig.addressPointer,
+      customTags: zapConfig.customTags,
+      relays: zapConfig.relays,
+    });
+  };
+
   const handleEmojiSelect = async (emoji: string, customEmoji?: EmojiTag) => {
     if (!conversation || !adapter) {
       console.error(
@@ -148,18 +160,6 @@ export function ChatMessageContextMenu({
     }
   };
 
-  const openZapWindow = () => {
-    if (!zapConfig || !zapConfig.supported) return;
-
-    addWindow("zap", {
-      recipientPubkey: zapConfig.recipientPubkey,
-      eventPointer: zapConfig.eventPointer,
-      addressPointer: zapConfig.addressPointer,
-      customTags: zapConfig.customTags,
-      relays: zapConfig.relays,
-    });
-  };
-
   return (
     <>
       <ContextMenu>

src/components/chat/RelaysDropdown.tsx

@@ -23,12 +23,15 @@ export function RelaysDropdown({ conversation }: RelaysDropdownProps) {
 
   // Get relays for this conversation (immutable pattern)
   const liveActivityRelays = conversation.metadata?.liveActivity?.relays;
+  const metadataRelays = conversation.metadata?.relays;
   const relays: string[] =
     Array.isArray(liveActivityRelays) && liveActivityRelays.length > 0
       ? liveActivityRelays
-      : conversation.metadata?.relayUrl
-        ? [conversation.metadata.relayUrl]
-        : [];
+      : Array.isArray(metadataRelays) && metadataRelays.length > 0
+        ? metadataRelays
+        : conversation.metadata?.relayUrl
+          ? [conversation.metadata.relayUrl]
+          : [];
 
   // Pre-compute normalized URLs and state lookups in a single pass (O(n))
   const relayData = relays.map((url) => {

src/components/chat/ReplyPreview.tsx

@@ -26,6 +26,9 @@ export const ReplyPreview = memo(function ReplyPreview({
   // Load the event being replied to (reactive - updates when event arrives)
   const replyEvent = use$(() => eventStore.event(replyToId), [replyToId]);
 
+  // Check if replying to thread root (NIP-10)
+  const isRoot = conversation.metadata?.rootEventId === replyToId;
+
   // Fetch event from relays if not in store
   useEffect(() => {
     if (!replyEvent) {
@@ -47,7 +50,7 @@ export const ReplyPreview = memo(function ReplyPreview({
   if (!replyEvent) {
     return (
       <div className="text-xs text-muted-foreground mb-0.5">
-        ↳ Replying to {replyToId.slice(0, 8)}...
+        ↳ Replying to {isRoot ? "thread root" : replyToId.slice(0, 8)}...
       </div>
     );
   }
@@ -59,10 +62,14 @@ export const ReplyPreview = memo(function ReplyPreview({
       title="Click to scroll to message"
     >
       <span className="flex-shrink-0">↳</span>
-      <UserName
-        pubkey={replyEvent.pubkey}
-        className="font-medium flex-shrink-0"
-      />
+      {isRoot ? (
+        <span className="font-medium flex-shrink-0">thread root</span>
+      ) : (
+        <UserName
+          pubkey={replyEvent.pubkey}
+          className="font-medium flex-shrink-0"
+        />
+      )}
       <div className="line-clamp-1 overflow-hidden flex-1 min-w-0">
         <RichText
           event={replyEvent}