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/lib/chatDraftPersistence.test.ts

@@ -0,0 +1,92 @@
+import { beforeEach, describe, expect, test } from 'bun:test';
+
+import {
+  clearChatDraft,
+  createChatDraftIdentity,
+  getChatDraftIdentityKey,
+  readChatDraft,
+  subscribeChatDraftDeletion,
+  writeChatDraft,
+} from './chatDraftPersistence';
+import { getDeferredSafeStorage } from '@/stores/utils/safeStorage';
+
+const storage = getDeferredSafeStorage();
+
+describe('chatDraftPersistence', () => {
+  beforeEach(() => {
+    storage.removeItem('openchamber.chatDrafts.v2');
+  });
+
+  test('isolates drafts by runtime, directory, and session', () => {
+    const first = createChatDraftIdentity('runtime-a', '/repo-a/', 'session-1')!;
+    const second = createChatDraftIdentity('runtime-b', '/repo-a', 'session-1')!;
+    const third = createChatDraftIdentity('runtime-a', '/repo-b', 'session-1')!;
+    writeChatDraft(first, 'first', ['file.ts']);
+    writeChatDraft(second, 'second', []);
+    writeChatDraft(third, 'third', []);
+
+    expect(readChatDraft(first)).toEqual({ text: 'first', confirmedMentions: new Set(['file.ts']) });
+    expect(readChatDraft(second).text).toBe('second');
+    expect(readChatDraft(third).text).toBe('third');
+  });
+
+  test('keeps new-session drafts separate from similarly named sessions', () => {
+    const newSession = createChatDraftIdentity('runtime-a', '/repo', null)!;
+    const namedSession = createChatDraftIdentity('runtime-a', '/repo', '__new__')!;
+
+    writeChatDraft(newSession, 'new session', []);
+    writeChatDraft(namedSession, 'named session', []);
+
+    expect(readChatDraft(newSession).text).toBe('new session');
+    expect(readChatDraft(namedSession).text).toBe('named session');
+  });
+
+  test('clears only the matching identity and notifies active composers', () => {
+    const deleted = createChatDraftIdentity('runtime-a', '/repo-a', 'session-1')!;
+    const retained = createChatDraftIdentity('runtime-a', '/repo-b', 'session-1')!;
+    const notifications: string[] = [];
+    const unsubscribe = subscribeChatDraftDeletion((identity) => notifications.push(identity.directory));
+    writeChatDraft(deleted, 'delete', []);
+    writeChatDraft(retained, 'retain', []);
+
+    clearChatDraft(deleted, true);
+    unsubscribe();
+
+    expect(readChatDraft(deleted).text).toBe('');
+    expect(readChatDraft(retained).text).toBe('retain');
+    expect(notifications).toEqual(['/repo-a']);
+  });
+
+  test('bounds persisted drafts by recency', () => {
+    for (let index = 0; index < 55; index += 1) {
+      const identity = createChatDraftIdentity('runtime-a', '/repo', `session-${index}`)!;
+      writeChatDraft(identity, `draft-${index}`, []);
+    }
+
+    const envelope = JSON.parse(storage.getItem('openchamber.chatDrafts.v2') ?? '{}') as { drafts?: object };
+    expect(Object.keys(envelope.drafts ?? {})).toHaveLength(50);
+  });
+
+  test('reuses a parsed envelope while the stored value is unchanged', () => {
+    const identity = createChatDraftIdentity('runtime-cache', '/repo', 'session-1')!;
+    const key = getChatDraftIdentityKey(identity);
+    storage.setItem('openchamber.chatDrafts.v2', JSON.stringify({
+      version: 2,
+      drafts: { [key]: { text: 'cached', confirmedMentions: [], touchedAt: 1 } },
+    }));
+    const originalParse = JSON.parse;
+    let parseCalls = 0;
+    JSON.parse = ((...args: Parameters<typeof JSON.parse>) => {
+      parseCalls += 1;
+      return originalParse(...args);
+    }) as typeof JSON.parse;
+
+    try {
+      expect(readChatDraft(identity).text).toBe('cached');
+      expect(readChatDraft(identity).text).toBe('cached');
+      expect(parseCalls).toBe(1);
+    } finally {
+      JSON.parse = originalParse;
+    }
+  });
+});