docs: document desktop features (Tier A + B) across catalog/README/TODO

- LOTUS_FEATURES.md: new "Desktop App Features" section (+ TOC) covering all
  desktop capabilities — no-sleep, jump list, thumbbar, SMTC, network awareness,
  rich notifications, Focus Assist, window chrome, update toast, toolbar reorder,
  draft indicator, recursive folder DnD.
- README.md: "Desktop-Specific Features" bullets under the Desktop App section.
- LOTUS_TODO.md: P5-35/41/56 → [~] IMPLEMENTED (Tier B); P5-48 → [~] (recursive
  folder upload; .lnk/Send-To scoped-out with rationale).

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

LOTUS_FEATURES.md

@@ -25,7 +25,8 @@ Last updated: June 2026.
 16. [Notifications](#notifications)
 17. [Server Integration](#server-integration)
 18. [Infrastructure](#infrastructure)
-19. [Key Custom Files](#key-custom-files)
+19. [Desktop App Features](#desktop-app-features)
+20. [Key Custom Files](#key-custom-files)
 
 ---
 
@@ -1161,6 +1162,59 @@ The `encUrlPreview` setting defaults to `true` rather than `false`. A security a
 
 ---
 
+## Desktop App Features
+
+Native capabilities of the Lotus Chat **Tauri v2** desktop app (Windows, macOS, Linux) on top of the shared web client. Web hooks live in `src/app/hooks/useTauri*.ts` (each no-ops in the browser) and call Rust commands in `cinny-desktop/src-tauri/src/native/*`. Windows-only pieces are `#[cfg(target_os = "windows")]`, compile-verified in CI (Windows runners).
+
+### Call Continuity — No-Sleep (P5-46)
+
+Holds the system awake (`SetThreadExecutionState`) while a voice/video call is active; releases on end. `useTauriCallPower` ↔ `native/power.rs`.
+
+### Windows Jump List (P5-36)
+
+Right-click the taskbar icon → a **Recent Rooms** list of your most-active rooms; each entry opens that room via the `matrix:` deep-link. `useTauriJumpList` ↔ `native/jumplist.rs` (`ICustomDestinationList`).
+
+### Taskbar Thumbnail Toolbar (P5-44)
+
+Hover the taskbar preview during a call → **Mute / Deafen / End Call** buttons. `useTauriThumbbar` ↔ `native/thumbbar.rs` (`ITaskbarList3` + a window subclass for `THBN_CLICKED`).
+
+### System Media Transport Controls — SMTC (P5-43)
+
+Exposes call status + a mute control to the Windows volume-flyout / media overlay (WinRT `SystemMediaTransportControls`). `useTauriSmtc` ↔ `native/smtc.rs`. _Experimental — may require an active audio session to surface._
+
+### Network Awareness (P5-49)
+
+Detects Windows connectivity changes (`INetworkListManager`) and nudges the Matrix client to reconnect (`retryImmediately`). `useTauriNetwork` ↔ `native/network.rs`.
+
+### Native Rich Notifications (P5-41 / P5-35)
+
+Windows toasts with **click-to-open-room** and **inline quick reply** (WinRT `ToastNotification`, in-process `Activated` event). Falls back to the standard toast otherwise. `useTauriToastActions` ↔ `native/toast.rs`; the desktop notification bridge routes room notifications to it.
+
+### Focus Assist Sync (P5-56)
+
+When Windows Focus Assist / Quiet Hours is active, Lotus suppresses its own notifications + sounds (reuses the quiet-hours gate). `useTauriFocusAssist` + `focusAssistActiveAtom` ↔ `native/focus_assist.rs` (`SHQueryUserNotificationState`).
+
+### Custom Window Chrome (P5-47)
+
+Opt-in (Settings → General → **Custom Window Chrome**): replaces the OS title bar with a TDS-styled titlebar (min / max / close + drag region), runtime-reversible via `set_decorations`. `features/desktop/TitleBar.tsx` + `useTauriWindowChrome` ↔ `native/chrome.rs`.
+
+### Proactive Update Toast (P5-40)
+
+Checks for a new desktop release every 12h and offers a one-click update. `TauriUpdateFeature` (ClientNonUIFeatures) + `useTauriUpdater`.
+
+### Cross-platform composer niceties
+
+- **Composer toolbar drag-reorder (P5-55)** — drag to reorder the composer buttons (Settings → General), via `@atlaskit/pragmatic-drag-and-drop`.
+- **Draft-saved indicator (P5-57)** — a subtle cue in the composer when the current room has a persisted draft.
+- **Recursive folder drag-drop (P5-48)** — drop a folder to upload every file inside it (all nesting levels), `utils/fileEntries.ts`.
+
+### Files
+
+- Web: `src/app/hooks/useTauri*.ts`, `src/app/components/TauriDesktopFeatures.tsx`, `src/app/features/desktop/TitleBar.tsx`, `src/app/features/room/DraftIndicator.tsx`, `src/app/utils/fileEntries.ts`, `src/app/state/{customWindowChrome,focusAssist}.ts`.
+- Native (`cinny-desktop`): `src-tauri/src/native/{power,jumplist,thumbbar,smtc,network,chrome,toast,focus_assist}.rs` + `native/mod.rs` (registered in `lib.rs`).
+
+---
+
 ## Key Custom Files
 
 | File                                                           | Purpose                                                                                     |