Add selectable ESP-NOW send path for accel/tap input.

Expose best_effort/fast/wait/reliable via UART, dashboard, and CLI so
loss vs latency can be compared under real multi-pod load.

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

main/proto/uart_messages.proto

@@ -42,6 +42,11 @@ enum MessageType {
    * online slaves), or on a slave clear local master/id binding only.
    */
   CLIENT_ID_MAP_RESET = 34;
+  /**
+   * Host → master: get/set slave ESP-NOW send path for accel/tap
+   * (best_effort / fast / wait / reliable).
+   */
+  INPUT_SEND_MODE = 35;
 }
 
 message UartMessage {
@@ -85,6 +90,8 @@ message UartMessage {
     BleStreamTick ble_stream_tick = 41;
     ClientIdMapResetRequest client_id_map_reset_request = 42;
     ClientIdMapResetResponse client_id_map_reset_response = 43;
+    InputSendModeRequest input_send_mode_request = 44;
+    InputSendModeResponse input_send_mode_response = 45;
   }
 }
 
@@ -167,6 +174,34 @@ message AccelStreamResponse {
   uint32 slaves_updated = 4;
 }
 
+/**
+ * Slave ESP-NOW TX path for ACCEL_SAMPLE / TAP_EVENT (debug A/B).
+ * Maps 1:1 to esp_now_core_send_*.
+ */
+enum InputSendMode {
+  INPUT_SEND_BEST_EFFORT = 0;
+  INPUT_SEND_FAST = 1;
+  INPUT_SEND_WAIT = 2;
+  INPUT_SEND_RELIABLE = 3;
+}
+
+// Host → master: get/set input send mode on slaves.
+// write=false: return last mode remembered on master (client_id ignored).
+// write=true: push mode via ESP-NOW (all_clients or one client_id).
+message InputSendModeRequest {
+  bool write = 1;
+  InputSendMode mode = 2;
+  uint32 client_id = 3;
+  bool all_clients = 4;
+}
+
+message InputSendModeResponse {
+  bool success = 1;
+  InputSendMode mode = 2;
+  uint32 client_id = 3;
+  uint32 slaves_updated = 4;
+}
+
 /** Host → master: read LiPo ADC voltages (master local and/or slaves via ESP-NOW). */
 message BatteryStatusRequest {
   /** 0 = master only; >0 = one slave; ignored when all_clients */