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/lib/aioespnow.py

@@ -0,0 +1,28 @@
+# aioespnow module for MicroPython on ESP32 and ESP8266
+# MIT license; Copyright (c) 2022 Glenn Moloney @glenn20
+# Vendored from micropython-lib/micropython/aioespnow
+
+import asyncio
+import espnow
+
+
+class AIOESPNow(espnow.ESPNow):
+    async def arecv(self):
+        yield asyncio.core._io_queue.queue_read(self)
+        return self.recv(0)
+
+    async def airecv(self):
+        yield asyncio.core._io_queue.queue_read(self)
+        return self.irecv(0)
+
+    async def asend(self, mac, msg=None, sync=None):
+        if msg is None:
+            msg, mac = mac, None
+        yield asyncio.core._io_queue.queue_write(self)
+        return self.send(mac, msg, sync)
+
+    def __aiter__(self):
+        return self
+
+    async def __anext__(self):
+        return await self.airecv()