feat(android): on-device OS notification capture (NotificationListenerService)

Add an Android backend to os_notification_listener.py so notifications on the
experimental Android-TV build drive the existing NotificationColorStripSource
LED effects (flash/pulse/sweep, per-app colors + sounds) at app-name parity
with the Windows/Linux backends.

A Kotlin NotificationListenerService forwards the posting app's display label
across the Chaquopy JNI boundary into a new push-based _AndroidBackend +
module-level push_notification() receiver; the existing color-strip pipeline,
per-app colors/filters, and history endpoint are reused unchanged.

- Python: _AndroidBackend (probed first), push_notification() receiver,
  _LinuxBackend.probe() hardened with is_linux() to exclude Android (which
  also reports platform.system() == "Linux").
- Android: LedGrabNotificationListener NLS — serial single-thread executor,
  full crash isolation around Python.getInstance(), label-only forwarding
  (never notification title/body), ongoing/group-summary/self-package noise
  filtering. Manifest service exported + gated by
  BIND_NOTIFICATION_LISTENER_SERVICE (no new uses-permission).
- UX: prompt-once notification-access + manual "Grant notification access"
  button wired into the D-pad focus chain (computed from visible controls);
  en/ru/zh strings.
- Tests: 11 isolated unit tests — module-global + tmp_path history isolation,
  push routing contract, callback-exception swallowing, None app-name, and a
  desktop-regression lock on backend selection order.
- Docs: README OS-support Android column (notification + audio cells),
  ANDROID-REVIEW status flipped to Implemented.

Zero new Python deps; no build.gradle.kts / Chaquopy pip changes.

ANDROID-REVIEW/android-missing-functionality.md

@@ -45,7 +45,7 @@ Python receiver engine mirroring that pattern.**
 | LED transports (network/USB-serial/BLE) | ✅ | ✅ (USB via Android driver, BLE via Android bridge) | No |
 | System metrics | psutil | ✅ CPU/RAM/battery/thermal via `/proc`, `/sys` (`AndroidMetricsProvider`) | No |
 | **Audio capture** | WASAPI / Sounddevice | ❌ no PortAudio | **Yes** |
-| **Notification capture** | WinRT / D-Bus | ❌ listener only Win/Linux | **Yes** |
+| Notification capture | WinRT / D-Bus | ✅ NotificationListenerService → `push_notification()` | No (implemented) |
 | Webcam capture | OpenCV | ❌ no OpenCV wheel | Yes (niche) |
 | GPU monitoring | NVML | ❌ no NVIDIA GPU | Marginal |
 | Capture from *another* Android phone | scrcpy/ADB | ❌ | Skip (redundant) |
@@ -70,7 +70,7 @@ Python receiver engine mirroring that pattern.**
   media and the device's own audio. Root mode (no MediaProjection) → mic-only.
 - 📄 **See `android-audio-capture-plan.md`** for the full implementation plan.
 
-### 🔔 Notification capture — **FEASIBLE, HIGH VALUE** ⭐ (planned)
+### 🔔 Notification capture — **IMPLEMENTED** ✅ (shipped)
 
 - **Android is the *best* platform for this:** `NotificationListenerService` is the native,
   event-push mechanism (no polling).
@@ -82,8 +82,13 @@ Python receiver engine mirroring that pattern.**
 - **Permission:** user enables "Notification access" in Settings (`ACTION_NOTIFICATION_LISTENER_SETTINGS`);
   no runtime-permission popup.
 - **Effort:** moderate. **Value:** high.
-- 📄 **Plan approved & detailed** — see `C:\Users\Alexei\.claude\plans\deep-enchanting-muffin.md`
-  (app-name parity; prompt-once permission UX).
+- ✅ **Implemented** on branch `feature/android-notification-capture`: a push-based
+  `_AndroidBackend` + module-level `push_notification()` in `os_notification_listener.py`,
+  a Kotlin `LedGrabNotificationListener` (NLS), and prompt-once permission UX. App-name
+  parity — only the resolved app label crosses the JNI boundary, never the notification
+  title/body. ⚠️ App labels can differ across OSes (Windows `display_name` / Linux D-Bus
+  `app_name` / Android `getApplicationLabel`), so desktop-configured per-app colors/filters
+  may need re-matching on Android.
 
 ### 📷 Webcam capture — **FEASIBLE, LOW VALUE**
 
@@ -128,7 +133,7 @@ Python receiver engine mirroring that pattern.**
 
 | Priority | Feature | Effort | Value | New Python deps | Status |
 | -------- | ------- | ------ | ----- | --------------- | ------ |
-| 1 | Notification capture | Moderate | High | None | **Plan approved** |
+| 1 | Notification capture | Moderate | High | None | **✅ Implemented** |
 | 2 | Audio capture | Moderate | High | None | **Plan written** (this folder) |
 | 3 | Automation: foreground-app condition | Moderate | Moderate | None | Idea |
 | 4 | Webcam capture (CameraX) | Moderate | Low | None | Idea |