perf: overhaul session loading, caching, and runtime isolation (#2360)

Improve OpenChamber responsiveness under large session workloads while fixing
cache, synchronization, and persistence correctness across runtimes, projects,
directories, and worktrees.

- prioritize selected and visible sessions during bootstrap and defer
  non-critical enrichment work
- reduce redundant message loading, event processing, store publication, and
  hidden sidebar work
- prevent stale session and message requests from overwriting newer
  authoritative state
- preserve existing data when authoritative fetches fail instead of treating
  failures as successful empty responses
- scope session materialization, messages, drafts, queues, todos, pins,
  permissions, folders, tabs, Git state, and pull request data by runtime and
  directory identity
- harden runtime switching, reconnect, cleanup, mutation reconciliation, and
  persisted-state ordering
- preserve live subagent Task linkage when metadata arrives after an older
  message request or while streaming parts are suspended
- coalesce overlapping tail refreshes without losing newer refresh demand
- improve cold-session loading by moving deferrable work out of the critical
  bootstrap path
- isolate URL authentication, mobile credentials, native secrets, and other
  runtime-owned state across endpoint changes
- bound long-lived caches and remove avoidable allocations from event and
  rendering hot paths
- limit virtualization to archive collections where it improves rendering
  without disrupting active sidebar layout
- stabilize session folders, pin ordering, expanded state, and persisted
  sidebar behavior
- open skill files through the same secure editor and outside-workspace grant
  flow used by file navigation, including worktree sessions
- expand regression coverage for stale completions, runtime collisions,
  reconnect behavior, persistence races, authoritative empty results, and
  subagent refresh ordering
- document the updated synchronization, cache ownership, performance, and
  runtime-isolation invariants

packages/ui/src/apps/mobileWidgetSnapshot.ts

@@ -5,6 +5,7 @@ import { useUIStore } from '@/stores/useUIStore';
 import { resolveGlobalSessionDirectory, useGlobalSessionsStore } from '@/stores/useGlobalSessionsStore';
 import { useProjectsStore } from '@/stores/useProjectsStore';
 import { useNotificationStore } from '@/sync/notification-store';
+import { getRuntimeKey } from '@/lib/runtime-switch';
 
 /**
  * Builds the lightweight session overview the native iOS widgets render (home medium,
@@ -26,6 +27,8 @@ export interface MobileWidgetSession {
 }
 
 export interface MobileWidgetSnapshot {
+  /** Runtime instance that owns all session IDs and paths in this snapshot. */
+  runtimeKey: string;
   /** Count of sessions needing attention — same signal that drives the app-icon badge. */
   attentionCount: number;
   /** Most-recently-updated top-level sessions, newest first (capped for the medium widget). */
@@ -97,7 +100,7 @@ export const buildMobileWidgetSnapshot = (): MobileWidgetSnapshot => {
     .slice(0, RECENT_LIMIT)
     .map(({ id, title, unread, project }) => ({ id, title, unread, project }));
 
-  return { attentionCount, recentSessions };
+  return { runtimeKey: getRuntimeKey(), attentionCount, recentSessions };
 };
 
 const SNAPSHOT_GLOBAL_KEY = '__OPENCHAMBER_WIDGET_SNAPSHOT__';