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/views/FilesView.tsx

@@ -567,9 +567,9 @@ const FileRow: React.FC<FileRowProps> = ({
             onOpenChange={(open) => setContextMenuPath(open ? node.path : null)}
           >
             <DropdownMenuTrigger asChild>
-              <Button 
-                variant="ghost" 
-                size="icon" 
+              <Button
+                variant="ghost"
+                size="icon"
                 className="size-6"
                 onClick={handleMenuButtonClick}
               >
@@ -810,7 +810,6 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
   const openPaths = useFilesViewTabsStore((state) => (root ? (state.byRoot[root]?.openPaths ?? EMPTY_PATHS) : EMPTY_PATHS));
   const selectedPath = useFilesViewTabsStore((state) => (root ? (state.byRoot[root]?.selectedPath ?? null) : null));
   const expandedPaths = useFilesViewTabsStore((state) => (root ? (state.byRoot[root]?.expandedPaths ?? EMPTY_PATHS) : EMPTY_PATHS));
-  const addOpenPath = useFilesViewTabsStore((state) => state.addOpenPath);
   const removeOpenPath = useFilesViewTabsStore((state) => state.removeOpenPath);
   const removeOpenPathsByPrefix = useFilesViewTabsStore((state) => state.removeOpenPathsByPrefix);
   const removeExpandedPathsByPrefix = useFilesViewTabsStore((state) => state.removeExpandedPathsByPrefix);
@@ -922,6 +921,7 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
   const diagramEditorRef = React.useRef<React.ComponentRef<typeof DiagramEditor>>(null);
   const lastLoadedFileStatRef = React.useRef<FileStatSnapshot | null>(null);
   const activeFileLoadIdRef = React.useRef(0);
+  const loadingFilePathRef = React.useRef<string | null>(null);
   const [autoSaveStatus, setAutoSaveStatus] = React.useState<'idle' | 'saved'>('idle');
   const [diagramSaved, setDiagramSaved] = React.useState(false);
   const [autoSaveEnabled, setAutoSaveEnabled] = React.useState(getInitialAutoSaveEnabled);
@@ -1952,7 +1952,6 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
 
     if (root) {
       setSelectedPath(root, node.path);
-      addOpenPath(root, node.path);
       void ensurePathVisible(node.path, false);
     }
 
@@ -1966,7 +1965,7 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
     if (isMobile) {
       setShowMobilePageContent(true);
     }
-  }, [addOpenPath, ensurePathVisible, isDirty, isMobile, root, setSelectedPath]);
+  }, [ensurePathVisible, isDirty, isMobile, root, setSelectedPath]);
 
   React.useEffect(() => {
     if (!selectedFile?.path) {
@@ -1979,16 +1978,23 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
   React.useEffect(() => {
     if (!selectedFile) {
       activeFileLoadIdRef.current += 1;
+      loadingFilePathRef.current = null;
       setFileLoading(false);
       return;
     }
 
-    if (loadedFilePath === selectedFile.path) {
+    if (loadedFilePath === selectedFile.path || loadingFilePathRef.current === selectedFile.path) {
       return;
     }
 
     // Selection changes are guarded; this effect is also what restores persisted tabs on mount.
-    void loadSelectedFile(selectedFile);
+    const loadingPath = selectedFile.path;
+    loadingFilePathRef.current = loadingPath;
+    void loadSelectedFile(selectedFile).finally(() => {
+      if (loadingFilePathRef.current === loadingPath) {
+        loadingFilePathRef.current = null;
+      }
+    });
   }, [loadSelectedFile, loadedFilePath, selectedFile]);
 
   // Sync isDirty to a ref so the polling interval can read the latest value
@@ -2192,7 +2198,7 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
   const getFileStatus = React.useCallback((path: string): FileStatus | null => {
     // Check open status
     if (openPaths.includes(path)) return 'open';
-    
+
     // Check git status
     if (gitStatus?.files) {
       const relative = path.startsWith(root + '/') ? path.slice(root.length + 1) : path;
@@ -2210,7 +2216,7 @@ export const FilesView: React.FC<FilesViewProps> = ({ mode = 'full' }) => {
     if (!gitStatus?.files) return null;
     const relativeDir = dirPath.startsWith(root + '/') ? dirPath.slice(root.length + 1) : dirPath;
     const prefix = relativeDir ? `${relativeDir}/` : '';
-    
+
     let modified = 0, added = 0;
     for (const f of gitStatus.files) {
       if (f.path.startsWith(prefix)) {