feat(inbox): auto-select next item after archiving the selected one

Archiving the currently selected inbox item used to clear the selection
and leave the detail panel empty, forcing the user to click the next
item to keep going. Pick the next (older) item from the deduplicated
list, falling back to the previous (newer) one when archiving at the
bottom, and only clear when nothing is left.

Route the detail panel's onDone path through the same handleArchive so
the auto-select behavior is shared.

Co-authored-by: multica-agent <github@multica.ai>

packages/views/inbox/components/inbox-page.tsx

@@ -144,8 +144,17 @@ export function InboxPage() {
   };
 
   const handleArchive = (id: string) => {
-    const archived = items.find((i) => i.id === id);
-    if (archived && (archived.issue_id ?? archived.id) === selectedKey) setSelectedKey("");
+    const idx = items.findIndex((i) => i.id === id);
+    const archived = idx >= 0 ? items[idx] : null;
+    const wasSelected =
+      !!archived && (archived.issue_id ?? archived.id) === selectedKey;
+    if (wasSelected) {
+      // List is sorted newest-first; prefer the next (older) item, fall back
+      // to the previous (newer) one when archiving at the bottom, and only
+      // clear the selection when nothing else is left.
+      const next = items[idx + 1] ?? items[idx - 1] ?? null;
+      setSelectedKey(next ? (next.issue_id ?? next.id) : "");
+    }
     archiveMutation.mutate(id, {
       onError: () => toast.error(t(($) => $.errors.archive_failed)),
     });
@@ -265,10 +274,7 @@ export function InboxPage() {
         setSelectedKey("");
       }}
       onDone={() => {
-        setSelectedKey("");
-        archiveMutation.mutate(selected.id, {
-          onError: () => toast.error(t(($) => $.errors.archive_failed)),
-        });
+        handleArchive(selected.id);
       }}
     />
   ) : selected ? (