feat: quick emoji reactions on hover, in-app notification toasts, mention pulse audit

P5-17: MessageQuickReactions moved from 3-dots menu to hover toolbar;
shows 5 recent emoji directly on hover. Clicking a quick-reaction also
closes any open emoji picker (setEmojiBoardAnchor). Line separator
removed from component.

P5-7: LotusToastContainer slides in from bottom-right when window is
focused — replaces OS notification for in-focus events. Correct room
path (DM vs home) derived from mDirectAtom. Invite toast routes to
inbox. 4s auto-dismiss. Full TDS styling via CSS custom properties.

P5-8: Confirmed already implemented upstream (MentionHighlightPulse,
0.6s scale+glow, one-shot, prefers-reduced-motion). Marked complete.

Code-review fixes: toast navigation used nonexistent /room/ route;
emoji picker stayed open after toolbar quick-reaction.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -150,6 +150,8 @@ Emoji reaction buttons styled for terminal mode via `button[data-reaction-key]`
 ### UX & Composer
 
 - **Message length counter**: A muted character counter appears just left of the send button while typing, disappearing when the composer is empty. Resets on room switch.
+- **Quick emoji reactions on hover**: The 5 most-recently-used emoji reactions appear directly in the message hover toolbar (between the emoji-board button and Reply), so reacting requires a single click rather than opening the 3-dots menu first. Clicking a quick-reaction also closes any open emoji picker. Powered by `useRecentEmoji` sourced from Matrix account data.
+- **In-app notification toasts**: When a message or invite notification fires and the browser window is focused, a slim TDS-styled toast card slides in from the bottom-right instead of triggering an OS notification. Card shows: 24px avatar (initials fallback), sender name in orange, truncated message body, room name, × dismiss, 4 s auto-dismiss. Clicking navigates directly to the correct room (DM or home path) or the invites inbox. OS notifications are unchanged when the window is not focused. Implemented in `src/app/features/toast/LotusToastContainer.tsx` + `src/app/state/toast.ts`.
 - **Collapsible long messages**: Messages exceeding ~20 lines are auto-collapsed with a "Read more ↓" button. Click to expand inline; a "Collapse ↑" button re-folds. Threshold (in lines) configurable in Settings → Appearance. Uses CSS `max-height` + `overflow: hidden` — works correctly with code blocks and embedded media. Respects `prefers-reduced-motion`.
 - **Message send animation**: Own sent messages fade and scale into the timeline (0.15 s ease-out: `scale(0.97)→scale(1)`, `opacity 0.4→1`). Incoming messages are unaffected. Respects `prefers-reduced-motion`.
 - **Right-click room context menu**: Expanded sidebar room context menu — **Mute** now opens a duration submenu (15 min / 1 hr / 8 hr / 24 hr / Indefinite) with auto-restore after the selected window; **Copy Room Link** copies the `matrix.to` URL with a "Copied!" flash; **Mark as Read** marks the room read to the latest event; plus Leave Room and Room Settings shortcuts.