chat: list /chat sessions from Claude's store; fix the dedicated-cwd routing

The /chat detail (ChatDetailPanel) now passes context 'chat' to usePiChat, so the
backend actually runs the session from claude_sessions (the earlier tag was on the
wrong component). The left panel (SessionList) now reads GET /chat/sessions —
Claude's own transcripts — instead of the old saved-sessions model. List-only:
rows display title/time/count; click-to-resume comes next.

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

src/workspaces/state/src/index.ts

@@ -5,6 +5,8 @@ export { useDashboardState } from './useDashboardState';
 export { usePiModels, useVisiblePiModels, useUserVisibleModels, useEnabledPiModels, modelKey } from './useModels';
 export type { ModelOption } from './useModels';
 export { useAccessPolicy } from './useAccessPolicy';
+export { useClaudeSessions } from './useClaudeSessions';
+export type { ClaudeSessionSummary } from './useClaudeSessions';
 export { useRecentModels } from './useRecentModels';
 export { usePlans } from './usePlans';
 export { useLandingPage } from './useLandingPage';

src/workspaces/state/src/useClaudeSessions.ts

@@ -0,0 +1,27 @@
+import { useQuery } from '@tanstack/react-query';
+import { useClient } from 'hooks/useClient';
+import { useAuth } from 'hooks/useAuth';
+
+export type ClaudeSessionSummary = {
+  id: string; // Claude session uuid (= transcript filename)
+  title: string;
+  cwd: string;
+  createdAt: string;
+  updatedAt: string;
+  messageCount: number;
+};
+
+/** The /chat route's sessions, read straight from Claude's own transcript store (source of truth). */
+export function useClaudeSessions() {
+  const client = useClient();
+  const { isAuthenticated } = useAuth();
+
+  const { data, isLoading, refetch } = useQuery<{ sessions: ClaudeSessionSummary[] }>({
+    queryKey: ['CLAUDE_SESSIONS'],
+    enabled: isAuthenticated,
+    queryFn: () => client.get<{ sessions: ClaudeSessionSummary[] }>('/chat/sessions'),
+    staleTime: 30 * 1000,
+  });
+
+  return { sessions: data?.sessions ?? [], isLoading, refetch };
+}