bell: notify a chat's page and list row, any chat, any time

Client half of the per-chat notification preference — DetailBar gets a bell
dropdown (every end of turn / only when input is needed / none), a global
useChatNotifications hook holds one connection to /api/chat/notify/ws for
the whole session so a background chat can still ring the bell and fire a
browser Notification, and the session list shows a badge on any row set to
notify. The server side (schema, the notify-delivery socket, the sidecar
signal at turn-end/plan-gate/question-gate) landed already in 5cba1b65,
swept in from a concurrent session sharing this working tree.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/workspaces/state/src/useClaudeSessions.ts

@@ -39,8 +39,12 @@ export type ClaudeSessionSummary = {
   model?: string | null;
   /** Whether this conversation is in plan mode. Absent on older rows; false is the default everywhere. */
   planMode?: boolean;
+  /** The bell preference — from `chat_notification_prefs`. Absent/`'none'` means no row yet. */
+  notifyPreference?: NotifyPreference;
 };
 
+export type NotifyPreference = 'every_turn' | 'input_needed' | 'none';
+
 // Display-ready message, matching the frontend ChatMessage union (rebuilt from Claude's transcript).
 export type ClaudeSessionMessage =
   | { role: 'user'; text: string }
@@ -167,6 +171,14 @@ export function useClaudeSessions(cwd?: string | null, options?: { all?: boolean
     [client, sessionQ, invalidate],
   );
 
+  const setNotifyPreference = useCallback(
+    async (id: string, preference: NotifyPreference) => {
+      await client.patch(`/chat/sessions/${id}/notify-pref${sessionQ}`, { preference });
+      invalidate();
+    },
+    [client, sessionQ, invalidate],
+  );
+
   return {
     sessions: data?.sessions ?? [],
     isLoading,
@@ -177,6 +189,7 @@ export function useClaudeSessions(cwd?: string | null, options?: { all?: boolean
     loadSession,
     deleteSession,
     renameSession,
+    setNotifyPreference,
     invalidate,
   };
 }