CHUNK #9: AI session storage layer (AgentController, AIStore, builders)

- Add packages/ai: AgentController (streaming + budget), SuggestionBuilder,
  NoteBuilder, AIStore (Dexie/IndexedDB), SuggestionMutation
- Fix createUlid to use monotonicFactory for reliable listSessions sort tiebreaker
- Extend outline system prompt with setting + characters context
- Add dexie dependency to packages/ai
- 188 tests passing (core 47, ui 5, editor 30, ai 71, exporters 22, web 13)

packages/ai/src/index.ts

@@ -25,6 +25,39 @@ export {
 } from "./client.js";
 export type { MeasuredBudget, StreamResult } from "./client.js";
 
+// Agent orchestration (CHUNK #9)
+export {
+  AgentController,
+  isRateLimitError,
+  DEFAULT_MAX_RETRIES,
+  DEFAULT_RETRY_BACKOFF_MS,
+} from "./agent.js";
+export type { AgentStatus, AgentCallbacks, AgentOptions } from "./agent.js";
+
+// Suggestion + note builders
+export { SuggestionBuilder } from "./suggestions.js";
+export type {
+  SuggestionKind,
+  SuggestionContext,
+  SuggestionPrompt,
+  SuggestionResult,
+} from "./suggestions.js";
+
+export { NoteBuilder } from "./notes.js";
+export type { NoteKind, NoteContext, NotePrompt, NoteResult } from "./notes.js";
+
+// Suggestion mutation (apply/revert)
+export { SuggestionMutation } from "./suggestion-mutation.js";
+export type { MutationResult } from "./suggestion-mutation.js";
+
+// AIStore — session/message/suggestion/note persistence (CHUNK #9)
+export {
+  AIStore,
+  createIndexedDBPersistence,
+  createInMemoryPersistence,
+} from "./ai-session.js";
+export type { AISessionPersistence, SessionRow } from "./ai-session.js";
+
 // Provider adapters + factory
 export { getProvider } from "./providers/adapters.js";