docs: threads + July batch across catalog/README/TODO/BUGS

- LOTUS_FEATURES: new Threads section (+TOC) — panel, summary chips, thread
  composer isolation, under-the-hood notes; entries for KaTeX math, opt-in
  encrypted-search cache, hardened session storage, Crypto Diagnostics.
- README: threads bullet (with the replies-move-to-panel release note), math,
  search-cache bullets.
- LOTUS_TODO: P3-8 → [~] implemented + 6-step live-QA checklist; P4-1 marked
  unblocked.
- LOTUS_BUGS: Needs Verification rows for P3-8 / P4-4 / P4-8 / session sync.

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

LOTUS_TODO.md

@@ -162,9 +162,17 @@ Status: `[ ]` pending · `[~]` in progress · `[x]` completed
 
 ---
 
-### [ ] P3-8 · Thread Panel (full side drawer)
+### [~] P3-8 · Thread Panel (full side drawer) — IMPLEMENTED (2026-07), ⚠️ AWAITING LIVE QA
 
-**⚠️ LARGEST FEATURE — 🟢 DESIGN COMPLETE (2026-07), READY FOR ITS OWN EXECUTION SESSION.** The full architecture (SDK-evidence-backed decisions, file inventory, 4-agent partition, risks, verification checklist) is in the Implementation Reference section below — no further planning needed, just a dedicated build session.  
+Built per the design below (4-agent build + 2-agent review). Gates green (tsc/eslint/build/tests). **Release note: threaded replies no longer render inline in the main timeline — roots show a "N replies" chip that opens the panel.**
+
+**Manual QA checklist (post-deploy):**
+1. Reply in Thread (message menu) → panel opens; send text/upload/emoji into it (appears pending → confirmed)
+2. Reply to a reply inside the panel → event carries `m.thread` + `m.in_reply_to` with `is_falling_back:false`
+3. Main timeline: root + chip only (replies absent); chip count/time updates live; unread badge appears for others' thread replies and clears after viewing the panel
+4. Room badge clears via normal markAsRead even with unread threads (unthreaded receipt)
+5. Reload: partitioning persists; encrypted-room threads decrypt (back-pagination too)
+6. Escape / × closes; mobile = fullscreen panel; switching rooms and back restores the open thread  
 **What:** A right-side drawer for threaded conversations. Currently "Reply in Thread" exists but there is no panel to read or write thread replies.
 
 Features:
@@ -208,7 +216,7 @@ Features:
 
 ### [ ] P4-1 · Thread Notification Mode Per-Thread (MSC3771)
 
-**Spec:** MSC3771 (stable). Depends on Thread Panel (#P3-8).  
+**Spec:** MSC3771 (stable). Depends on Thread Panel (#P3-8) — **NOW UNBLOCKED (P3-8 implemented 2026-07)**.  
 **What:** Per-thread notification toggle: "All messages" vs "Mentions only". Accessible from the thread panel header. Tracks unread counts separately per thread.  
 **[AUDIT REQUIRED]** — Implement after Thread Panel. Requires understanding how the SDK tracks per-thread unread counts.  
 **Complexity:** Medium (after thread panel exists).