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/chat/MessageList.tsx

@@ -16,7 +16,7 @@ import { useFeatureFlagsStore } from '@/stores/useFeatureFlagsStore';
 import { isHiddenUserMessage } from './message/hiddenUserMessage';
 import { FadeInDisabledProvider } from './message/FadeInOnReveal';
 import { hasPendingUserSendAnimation, consumePendingUserSendAnimation } from '@/lib/userSendAnimation';
-import { streamPerfCount, streamPerfMeasure } from '@/stores/utils/streamDebug';
+import { streamPerfCount, streamPerfMark, streamPerfMeasure } from '@/stores/utils/streamDebug';
 import type { StreamPhase } from './message/types';
 import { useGlobalSessionsStore } from '@/stores/useGlobalSessionsStore';
 import { useSessionParts } from '@/sync/sync-context';
@@ -885,6 +885,7 @@ const MessageListEntry = React.memo(({
     activeStreamingPhase,
     reviewTransferDirection,
 }: MessageListEntryProps) => {
+    streamPerfCount('ui.message_list_entry.render');
     if (entry.kind === 'ungrouped') {
         return (
             <UngroupedMessageRow
@@ -1264,6 +1265,7 @@ const MessageList = React.forwardRef<MessageListHandle, MessageListProps>(({
     scrollRef,
     directory,
 }, ref) => {
+    streamPerfMark('react.message_list_render');
     streamPerfCount('ui.message_list.render');
     const stickyUserHeader = useUIStore(state => state.stickyUserHeader);
     const chatRenderMode = useUIStore((state) => state.chatRenderMode);