feat(espnow): Pi bridge client, binary wire, and espnow-sender firmware

Replace serial/Wi-Fi driver transport paths with WebSocket bridge client,
binary espnow_wire delivery, device announce registry, and restructured
espnow-sender (AP + broadcast passthrough). Includes docs and tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

espnow-sender/README.md

@@ -1,7 +1,54 @@
-# espnow-sender
+# espnow-sender (ESP-NOW bridge)
 
-Minimal MicroPython project for receiving JSON over Microdot WebSocket.
+ESP32 firmware that relays **binary** ESP-NOW packets to/from led-controller over WebSocket.
 
-- WebSocket endpoint: `/ws`
-- Entry point: `main.py`
-- Message template: `msg.json`
+Layout matches **led-driver** so you deploy with **led-tool** from this directory:
+
+```
+espnow-sender/
+  src/          # uploaded to device root via --src
+    main.py
+    wifi_ap.py
+    util.py
+    espnow_wire.py
+  lib/          # uploaded to /lib via --lib
+    aioespnow.py
+    microdot/
+```
+
+## Deploy with led-tool
+
+```bash
+cd espnow-sender
+python ../led-tool/cli.py -p /dev/ttyUSB0 --src --lib -r -f
+```
+
+| Flag | Effect |
+|------|--------|
+| `--src` | Upload `./src` → device `:/` (`main.py`, `util.py`, `espnow_wire.py`) |
+| `--lib` | Upload `./lib` → device `/lib` (aioespnow, Microdot) |
+| `-r` | Reset after upload |
+| `-f` | Follow serial output |
+
+From **led-controller** root:
+
+```bash
+python led-tool/cli.py -p /dev/ttyUSB0 --src --lib -r -f
+```
+
+(run with `cwd` = `espnow-sender`, or `cd espnow-sender` first)
+
+Optional: `--force-upload` to ignore `file_hashes.json` on the device.
+
+## Runtime
+
+- **Wi-Fi access point** (default IP **192.168.4.1**): connect the Pi to the bridge SSID (`name` in `/settings.json`, e.g. `bridge-aabbccddeeff`)
+- WebSocket server: `/ws` on port **80** — set Pi `bridge_ws_url` to `ws://192.168.4.1/ws` (or the printed IP)
+- Optional `ap_password` in `/settings.json` (empty = open network)
+- Default Wi-Fi channel: **6** (Pi sends `BRIDGE_CH` on connect; updates AP + ESP-NOW STA)
+- Max **20** ESP-NOW peers (LRU eviction)
+
+## Protocol
+
+- [docs/espnow-architecture.md](../docs/espnow-architecture.md)
+- [docs/espnow-binary-protocol.md](../docs/espnow-binary-protocol.md)