fix: buffer NIP-29 messages until EOSE to prevent partial renders

The loadMessages observable was emitting on every event as they streamed
in before EOSE, causing multiple re-renders with partial message lists.
This resulted in incorrect scroll positions during initial chat load.

Now uses combineLatest with a BehaviorSubject to track EOSE state and
only emits the message list after the initial batch is fully loaded.
New messages after EOSE continue to trigger immediate updates.

https://claude.ai/code/session_0174r1Ddh5e2RuhHf2ZrFiNc

src/lib/chat/adapters/nip-29-adapter.ts

@@ -1,5 +1,10 @@
-import { Observable, firstValueFrom } from "rxjs";
-import { map, first, toArray } from "rxjs/operators";
+import {
+  Observable,
+  firstValueFrom,
+  BehaviorSubject,
+  combineLatest,
+} from "rxjs";
+import { map, first, toArray, filter as filterOp } from "rxjs/operators";
 import type { Filter } from "nostr-tools";
 import { nip19 } from "nostr-tools";
 import type { EventPointer, AddressPointer } from "nostr-tools/nip19";
@@ -332,6 +337,9 @@ export class Nip29Adapter extends ChatProtocolAdapter {
     const conversationId = `nip-29:${relayUrl}'${groupId}`;
     this.cleanup(conversationId);
 
+    // Track EOSE state - don't emit until initial batch is loaded
+    const eoseReceived$ = new BehaviorSubject<boolean>(false);
+
     // Start a persistent subscription to the group relay
     const subscription = pool
       .subscription([relayUrl], [filter], {
@@ -341,6 +349,7 @@ export class Nip29Adapter extends ChatProtocolAdapter {
         next: (response) => {
           if (typeof response === "string") {
             console.log("[NIP-29] EOSE received");
+            eoseReceived$.next(true);
           } else {
             console.log(
               `[NIP-29] Received event k${response.kind}: ${response.id.slice(0, 8)}...`,
@@ -352,9 +361,10 @@ export class Nip29Adapter extends ChatProtocolAdapter {
     // Store subscription for cleanup
     this.subscriptions.set(conversationId, subscription);
 
-    // Return observable from EventStore which will update automatically
-    return eventStore.timeline(filter).pipe(
-      map((events) => {
+    // Return observable that only emits after EOSE (prevents partial renders during initial load)
+    return combineLatest([eventStore.timeline(filter), eoseReceived$]).pipe(
+      filterOp(([, eose]) => eose), // Only emit after EOSE received
+      map(([events]) => {
         const messages = events.map((event) => {
           // Convert nutzaps (kind 9321) using nutzapToMessage
           if (event.kind === 9321) {