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/components/layout/SidebarFilesTree.tsx

@@ -1,4 +1,5 @@
 import React from 'react';
+import { getRuntimeKey } from '@/lib/runtime-switch';
 
 import { toast } from '@/components/ui';
 import {
@@ -121,20 +122,23 @@ type FileTreeCache = {
 };
 const FILE_TREE_CACHE_MAX_ROOTS = 8;
 const fileTreeCacheByRoot = new Map<string, FileTreeCache>();
+const fileTreeCacheKey = (root: string): string => JSON.stringify([getRuntimeKey(), root]);
 
 const touchCache = (root: string): FileTreeCache | null => {
-  const entry = fileTreeCacheByRoot.get(root);
+  const key = fileTreeCacheKey(root);
+  const entry = fileTreeCacheByRoot.get(key);
   if (!entry) return null;
   entry.touchedAt = Date.now();
   // Touch on read promotes the key to the end of the Map's iteration order,
   // so the oldest (front) entry is the next eviction candidate.
-  fileTreeCacheByRoot.delete(root);
-  fileTreeCacheByRoot.set(root, entry);
+  fileTreeCacheByRoot.delete(key);
+  fileTreeCacheByRoot.set(key, entry);
   return entry;
 };
 
 const getOrCreateCache = (root: string): FileTreeCache => {
-  const existing = fileTreeCacheByRoot.get(root);
+  const key = fileTreeCacheKey(root);
+  const existing = fileTreeCacheByRoot.get(key);
   if (existing) {
     existing.touchedAt = Date.now();
     return existing;
@@ -151,12 +155,12 @@ const getOrCreateCache = (root: string): FileTreeCache => {
     loadedDirs: new Set(),
     touchedAt: Date.now(),
   };
-  fileTreeCacheByRoot.set(root, created);
+  fileTreeCacheByRoot.set(key, created);
   return created;
 };
 
 const dropCacheForRoot = (root: string): void => {
-  fileTreeCacheByRoot.delete(root);
+  fileTreeCacheByRoot.delete(fileTreeCacheKey(root));
 };
 
 const getFileIcon = (filePath: string, extension?: string): React.ReactNode => {