chore: surface swallowed errors + remove dead session_renamed paths

Swallowed-error logging (audit Feature 3):
- file_index.ts:36-37 (git mtime probes): comment — best-effort, project
  may not be a git repo.
- useUserEvents.ts:44 / 53 (ws.close on error / unmount): comments —
  best-effort, socket may already be closing.
- RightRail.tsx:38 (localStorage write): comment — best-effort, quota or
  private mode.
- App.tsx:21 (api.sessions.get for RightRail projectId): replaced silent
  catch with console.warn.
- Session.tsx:38, 41 (session fetch + project list for breadcrumb):
  replaced silent catches with console.warn.

H1: ProjectSidebar.tsx:189 — dropped the local sessionEvents.emit
({type:'session_renamed'}) after PATCH. Server publishes via
broker.publishUser since v1.4; useUserEvents forwards.

H2: useSessionStream.ts session_renamed case removed (dead — no
server code path publishes session_renamed on the per-session WS
channel; only user channel via broker.publishUser). Also dropped the
session_renamed variant from WsFrame (in apps/web/src/api/types.ts)
to keep the discriminated-union switch exhaustive.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/hooks/useSessionStream.ts

@@ -2,6 +2,10 @@ import { useEffect, useRef, useState } from 'react';
 import type { Message, WsFrame } from '@/api/types';
 import { sessionEvents } from './sessionEvents';
 
+// session_renamed frame removed from WsFrame — it was declared but never
+// published on the per-session WS channel (server publishes via broker.publishUser
+// since v1.4). chat_renamed remains; auto_name.ts publishes it on session WS.
+
 interface State {
   messages: Message[];
   connected: boolean;
@@ -118,14 +122,6 @@ function applyFrame(state: State, frame: WsFrame): State {
         messages: state.messages.filter((m) => !removeSet.has(m.id)),
       };
     }
-    case 'session_renamed': {
-      sessionEvents.emit({
-        type: 'session_renamed',
-        session_id: frame.session_id,
-        name: frame.name,
-      });
-      return state;
-    }
     case 'chat_renamed': {
       sessionEvents.emit({
         type: 'chat_updated',