Added ECHO cmd and fixed some timing issues

main/proto/esp_now_messages.proto

@@ -24,12 +24,27 @@ enum EspNowMessageType {
   ESPNOW_BATTERY_REPORT = 16;
   ESPNOW_SET_TAP_NOTIFY = 17;
   ESPNOW_TAP_EVENT = 18;
+  ESPNOW_ECHO_PING = 19;
+  ESPNOW_ECHO_PONG = 20;
 }
 
 message EspNowUnicastTest {
   uint32 seq = 1;
 }
 
+/** Master → slave: echo ping (host ts + master monotonic time for RTT). */
+message EspNowEchoPing {
+  uint64 host_timestamp_us = 1;
+  /** esp_timer_get_time() (µs since boot) when master forwarded this message. */
+  uint64 master_time_us = 2;
+}
+
+/** Slave → master: echo ping payload unchanged. */
+message EspNowEchoPong {
+  uint64 host_timestamp_us = 1;
+  uint64 master_time_us = 2;
+}
+
 /** Master → slave: locate pod (LED ring R/G/B ×3 @ full brightness). */
 message EspNowFindMe {
   /** 0 = any slave; otherwise only slave_id must match */
@@ -43,6 +58,8 @@ message EspNowRestart {
 
 message EspNowDiscover {
   uint32 network = 1;
+  /** Master is in an OTA session (UART upload or ESP-NOW distribution). */
+  bool master_ota_pending = 2;
 }
 
 message EspNowSlavePresence {
@@ -158,5 +175,7 @@ message EspNowMessage {
     EspNowBatteryReport battery_report = 17;
     EspNowTapNotify tap_notify = 18;
     EspNowTapEvent tap_event = 19;
+    EspNowEchoPing echo_ping = 20;
+    EspNowEchoPong echo_pong = 21;
   }
 }