chat: retire the old saved-session store (Stage 4a)

Deletes all session persistence that isn't Claude's native transcript store, per
the "only harness-native session management survives" rule.

Backend: delete api/pi/storage.ts (meta.json+messages.json file store), the
api/saved-sessions router (+ unmount), the /pi/sessions REST endpoints, and the
storage.save/loadSession calls in the chat WS handler (in-memory session-manager
stays for live turns; no disk persistence — Claude's transcript is the record).
Also drops the Postgres saved_sessions layer: schema/chat.ts, queries/saved-sessions.ts,
its types and re-exports.

Frontend: delete state/useSavedSessions, ChatList, and the ChatHistory Widget
(all pure saved-session UI); slim ChatHeader to a label; strip the auto-load-latest
+ Save wiring from ChatPanelWrapper and ChatDetailPanel; drop the old resume path
from useChat and SessionListPage; remove the /chat/saved/:id route and the
useInitialData prefetch.

Behavior removed (intended): the Save-session button, email/project panels
auto-resuming the last chat, and /chat/saved/:id. /chat itself is unchanged —
already fully on Claude transcripts. The orphaned saved_sessions Postgres table
is dropped on the next `bun db:push`.

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

src/servers/hono.ts

@@ -30,7 +30,6 @@ import { browserRouter } from './api/browser/router';
 import { desktopRouter } from './api/desktop/rest';
 import { appsRouter, appServeRouter } from './api/apps';
 import { bugReportRouter } from './api/bug-report/bug-report';
-import { savedSessionsRouter } from './api/saved-sessions/saved-sessions';
 import { chatRouter } from './api/chat/chat';
 import { pipelineJobsRouter } from './api/tasks/pipeline-jobs-routes';
 import { broadcastPanelRefresh } from './api/terminal/websocket';
@@ -103,7 +102,6 @@ protectedRouter.route('/channels', channelsRouter);
 protectedRouter.route('/browser', browserRouter);
 protectedRouter.route('/apps', appsRouter);
 protectedRouter.route('/bug-report', bugReportRouter);
-protectedRouter.route('/saved-sessions', savedSessionsRouter);
 protectedRouter.route('/chat', chatRouter);
 protectedRouter.route('/pipeline-jobs', pipelineJobsRouter);
 protectedRouter.route('/jobs', pipelineJobsRouter); // unified jobs API (script + pipeline); /pipeline-jobs kept for the existing UI