Assign sequential pod IDs from the master with NVS-stable bindings.

Replaces MAC-byte self-IDs with master allocation (1–255), slave preferred-ID reconnect, debug reset via UART/UI, and rate-limited ASSIGN to avoid ESP-NOW NO_MEM storms.

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

main/proto/esp_now_messages.proto

@@ -27,6 +27,10 @@ enum EspNowMessageType {
   ESPNOW_ECHO_PING = 19;
   ESPNOW_ECHO_PONG = 20;
   ESPNOW_SET_TAP_CONFIG = 21;
+  /** Master → slave: assigned logical client id after join/presence. */
+  ESPNOW_ASSIGN_ID = 22;
+  /** Master → slave: forget persisted master/id binding (debug reset). */
+  ESPNOW_CLEAR_ID_BINDING = 23;
 }
 
 message EspNowUnicastTest {
@@ -67,11 +71,20 @@ message EspNowSlavePresence {
   uint32 network = 1;
   bytes mac = 2;
   uint32 version = 3;
+  /** Preferred id from NVS for this master (0 = none / unbound). */
   uint32 slave_id = 4;
   bool available = 5;
   bool used = 6;
 }
 
+/** Master → slave: definitive logical client id for this session/master. */
+message EspNowAssignId {
+  uint32 assigned_id = 1;
+}
+
+/** Master → slave: clear persisted {master_mac, assigned_id} binding. */
+message EspNowClearIdBinding {}
+
 message EspNowAccelDeadzone {
   uint32 deadzone = 1;
   uint32 client_id = 2; // 0 = all slaves; otherwise only matching slave_id applies
@@ -193,5 +206,7 @@ message EspNowMessage {
     EspNowEchoPing echo_ping = 20;
     EspNowEchoPong echo_pong = 21;
     EspNowTapConfig tap_config = 22;
+    EspNowAssignId assign_id = 23;
+    EspNowClearIdBinding clear_id_binding = 24;
   }
 }