docs: mark P4-8 (search cache) + session-atomicity as shipped

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

LOTUS_BUGS.md

@@ -139,7 +139,7 @@ retry … AbortError: Restart delayed event timed out before the HS responded`,
 ### Security & Privacy
 
 - **N97 — Access token stored in plaintext `localStorage`** (`state/sessions.ts`), vulnerable to XSS; device ID likewise. Architectural — needs a token-protection / session-storage redesign.
-- **Session writes are non-atomic and not cross-tab synced** (`state/sessions.ts`) — risks inconsistent state / races across tabs.
+- ~~**Session writes are non-atomic and not cross-tab synced**~~ — **done (2026-07):** atomic single-key `cinny_session_v1` blob (legacy-key migration + dual-write) + `subscribeSessionChanges`/`useSessionSync` cross-tab reload. (The plaintext-token concern in N97 above is the remaining, separate architectural item.)
 - **Persisted PII without encryption:** user status message + expiry (`settings/account/Profile.tsx`), unsent composer drafts (`room/RoomInput.tsx`). Leak risk on shared devices.
 
 ### PWA / Offline / Notifications

LOTUS_TODO.md

@@ -209,10 +209,9 @@ Features:
 **What:** Replace the manual "load more" button with an automated, virtualized infinite scroll for search results.  
 **Status:** Done in a prior session — `MessageSearch.tsx` already uses `useVirtualizer` (~line 336) over the result groups AND auto-fetches the `nextToken` page when the last virtual item scrolls into view (~line 469) via `useInfiniteQuery`. Nothing left to build.
 
-### [ ] P4-8 · Encrypted Message Search Indexing & Caching
+### [~] P4-8 · Encrypted Message Search Indexing & Caching — IMPLEMENTED (2026-07), opt-in
 
-**What:** Implement a persistent local cache for search results, optimized for encrypted rooms.  
-**Approach:** Use `IndexedDB` to store search metadata (event IDs, timestamps) to prevent redundant server-side decryption/fetching.
+**Shipped:** `src/app/utils/searchCache.ts` — raw-IndexedDB per-room index (`lotus-search-cache`) of decrypted search rows + coverage markers, merged into local search (in-memory-wins dedupe). **Opt-in, default OFF** (stores plaintext at rest) with a privacy note, Clear button, and logout wipe. Awaiting live QA (LOTUS_BUGS AW / P4-8 row).
 
 ### [~] P4-1 · Thread Notification Mode Per-Thread — IMPLEMENTED (2026-07), ⚠️ AWAITING LIVE QA