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/mobile/ios/App/OpenChamberNotificationService/NotificationService.swift

@@ -37,6 +37,7 @@ class NotificationService: UNNotificationServiceExtension {
         guard let defaults = UserDefaults(suiteName: Self.appGroup) else { return }
 
         var snapshot: [String: Any] = [
+            "runtimeKey": request.content.userInfo["runtimeKey"] as? String ?? "",
             "attentionCount": 0,
             "recentSessions": [],
         ]
@@ -46,6 +47,16 @@ class NotificationService: UNNotificationServiceExtension {
             snapshot = stored
         }
 
+        if let pushRuntimeKey = request.content.userInfo["runtimeKey"] as? String,
+           !pushRuntimeKey.isEmpty,
+           snapshot["runtimeKey"] as? String != pushRuntimeKey {
+            snapshot = [
+                "runtimeKey": pushRuntimeKey,
+                "attentionCount": 0,
+                "recentSessions": [],
+            ]
+        }
+
         // Attention count: authoritative server value carried in aps.badge.
         if let badge = request.content.badge as? Int {
             snapshot["attentionCount"] = badge

packages/mobile/ios/App/OpenChamberWidget/WidgetShared.swift

@@ -17,10 +17,11 @@ struct WidgetSession: Codable, Identifiable, Hashable {
 /// The session overview snapshot. Mirrors MobileWidgetSnapshot (same field names) so the
 /// JSON the app stores decodes directly.
 struct WidgetSnapshot: Codable {
+    var runtimeKey: String?
     let attentionCount: Int
     let recentSessions: [WidgetSession]
 
-    static let empty = WidgetSnapshot(attentionCount: 0, recentSessions: [])
+    static let empty = WidgetSnapshot(runtimeKey: nil, attentionCount: 0, recentSessions: [])
 }
 
 enum WidgetStore {