fix(threads): harden threads list after review

Address findings from 3 review agents on the Threads list panel:

- Last-activity accuracy (SDK): sort key and the "last reply <time>"
  label now use thread.replyToEvent.getTs() (server bundle latest_event)
  instead of lastReply(), which returns the ROOT time until each thread's
  replies lazily paginate (or permanently on fetch error). Applied to the
  hook signature too.

- Live-refresh completeness (correctness): the useRoomThreads signature
  now includes thread.length and the root event's replacingEventId, so a
  mid-thread redaction (reply count) and a root-message edit (row snippet)
  refresh the row live instead of going stale.

- a11y: the row's aria-label was the button's whole accessible name,
  hiding the snippet/count/unread from screen readers. It now describes
  the thread ("Open thread by <name>, unread, N replies, last reply ..").

- Unread badge: replaced the bare green dot (Success = the mention color)
  with the app-wide UnreadBadge, using the Highlight count so mentions
  render red and ordinary unread renders secondary, matching room-nav.

- Hover/focus affordance: the clickable row moved its inline styles to a
  css class with token-based :hover / :active backgrounds.

- Participant pile now also includes the last replier from the bundle.

- Stabilized the panel's onClose/onOpenThread with useCallback so its
  Escape listener isn't re-subscribed every Room render. Added
  filter->sort pipeline + all/participating immutability tests.

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

LOTUS_FEATURES.md

@@ -869,7 +869,7 @@ A right-side drawer (mirrors the members drawer; fullscreen on mobile) with the
 
 A room-level overview of **all** threads, opened from a **Threads** button (🧵) in the room header (mirrors the gallery/widgets toggles). Each row shows the root sender + message snippet, an unread dot, a meta line ("N replies · last reply 5m ago") and a **participant avatar pile**. A segmented **filter** (All / Unread / Participating — the latter via `thread.hasCurrentUserParticipated`) and **sort** (Recent / Oldest, by last-reply time) sit in the toolbar; both persist in localStorage (`cinny_threads_filter_v1` / `cinny_threads_sort_v1`). Clicking a row opens the existing single-thread `ThreadPanel` (reuses `setActiveThreadId`), and reading it clears the row's unread badge live. The list stays live via `ThreadEvent.New/NewReply/Update/Delete` + `RoomEvent.UnreadNotifications` and is virtualized for busy rooms.
 
-- Files: `features/room/thread/ThreadsListPanel.tsx`, `hooks/useRoomThreads.ts` (populates via `room.fetchRoomThreads()` + `room.getThreads()`), `state/threadsList.ts`, pure filter/sort in `utils/threadList.ts` (`filterThreads`/`sortThreads`, unit-tested). Reuses `useThreadSummary` data, `UnreadBadge`, `StackedAvatar`/`useMemberAvatar`, and the Bookmarks-panel segmented-control pattern.
+- Files: `features/room/thread/ThreadsListPanel.tsx`, `hooks/useRoomThreads.ts` (populates via `room.fetchRoomThreads()` + `room.getThreads()`; last-activity + reply-count + root-edit signature so rows refresh live), `state/threadsList.ts`, pure filter/sort in `utils/threadList.ts` (`filterThreads`/`sortThreads`, unit-tested). Unread mirrors `useThreadSummary`'s logic (`getThreadUnreadNotificationCount`, muted threads zeroed) and renders the app-wide `UnreadBadge` (red for mentions via the Highlight count). Reuses `StackedAvatar`/`useMemberAvatar` for the participant pile and the Bookmarks-panel segmented-control pattern.
 
 ### Summary Chips