chat: delete sessions + auto-refresh the /chat list after each turn

DELETE /chat/sessions/:id removes Claude's transcript file; the list gets a
per-row delete button. The list also invalidates on turn-complete so new and
continued sessions surface without a manual refresh.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/workspaces/state/src/useClaudeSessions.ts

@@ -1,7 +1,10 @@
-import { useQuery } from '@tanstack/react-query';
+import { useQuery, useQueryClient } from '@tanstack/react-query';
+import { useCallback } from 'react';
 import { useClient } from 'hooks/useClient';
 import { useAuth } from 'hooks/useAuth';
 
+const QUERY_KEY = ['CLAUDE_SESSIONS'];
+
 export type ClaudeSessionSummary = {
   id: string; // Claude session uuid (= transcript filename)
   title: string;
@@ -22,10 +25,11 @@ export type ClaudeSessionDetail = { id: string; model: string; cwd: string; mess
 /** The /chat route's sessions, read straight from Claude's own transcript store (source of truth). */
 export function useClaudeSessions() {
   const client = useClient();
+  const queryClient = useQueryClient();
   const { isAuthenticated } = useAuth();
 
   const { data, isLoading, refetch } = useQuery<{ sessions: ClaudeSessionSummary[] }>({
-    queryKey: ['CLAUDE_SESSIONS'],
+    queryKey: QUERY_KEY,
     enabled: isAuthenticated,
     queryFn: () => client.get<{ sessions: ClaudeSessionSummary[] }>('/chat/sessions'),
     staleTime: 30 * 1000,
@@ -33,5 +37,15 @@ export function useClaudeSessions() {
 
   const loadSession = (id: string) => client.get<ClaudeSessionDetail>(`/chat/sessions/${id}`);
 
-  return { sessions: data?.sessions ?? [], isLoading, refetch, loadSession };
+  const invalidate = useCallback(() => queryClient.invalidateQueries({ queryKey: QUERY_KEY }), [queryClient]);
+
+  const deleteSession = useCallback(
+    async (id: string) => {
+      await client.delete(`/chat/sessions/${id}`);
+      invalidate();
+    },
+    [client, invalidate],
+  );
+
+  return { sessions: data?.sessions ?? [], isLoading, refetch, loadSession, deleteSession, invalidate };
 }