feat(espnow): ping request/response with jittered delay

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

src/espnow_wire.py

@@ -9,6 +9,8 @@ MSG_ANNOUNCE = 0x01
 MSG_GROUPS = 0x02
 MSG_CMD = 0x03
 MSG_GROUP_CMD = 0x04
+MSG_PING_REQ = 0x05
+MSG_PING_RSP = 0x06
 
 BROADCAST_MAC = b"\xff\xff\xff\xff\xff\xff"
 
@@ -104,6 +106,29 @@ def cmd_envelope(payload):
     return env[:need], save
 
 
+def pack_ping_req(ping_id):
+    body = struct.pack("<I", int(ping_id) & 0xFFFFFFFF)
+    return _pack_header(MSG_PING_REQ, body)
+
+
+def parse_ping_req(payload):
+    if len(payload) >= 2 and payload[0] == WIRE_MAGIC:
+        if payload[1] != MSG_PING_REQ:
+            return None
+        body = payload[2:]
+    else:
+        body = payload
+    if len(body) < 4:
+        return None
+    return struct.unpack("<I", body[:4])[0]
+
+
+def pack_ping_rsp(ping_id, name):
+    name_b = name.encode("utf-8")
+    body = struct.pack("<I", int(ping_id) & 0xFFFFFFFF) + bytes([len(name_b)]) + name_b
+    return _pack_header(MSG_PING_RSP, body)
+
+
 def wire_msg_type(payload):
     if len(payload) >= 2 and payload[0] == WIRE_MAGIC:
         return payload[1]