Add UART LED_RING command for progress bar, digits, and clear.

Stop the main-loop digit demo so host-driven display persists; expose
clear/progress/digit modes with RGB and intensity via protobuf and goTool.

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

main/proto/uart_messages.proto

@@ -13,6 +13,7 @@ enum MessageType {
   CLIENT_INPUT = 5;
   ACCEL_DEADZONE = 6;
   ESPNOW_UNICAST_TEST = 7;
+  LED_RING = 8;
   OTA_START = 16;
   OTA_PAYLOAD = 17;
   OTA_END = 18;
@@ -39,6 +40,8 @@ message UartMessage {
     EspNowUnicastTestResponse espnow_unicast_test_response = 14;
     OtaSlaveProgressRequest ota_slave_progress_request = 15;
     OtaSlaveProgressResponse ota_slave_progress_response = 16;
+    LedRingProgressRequest led_ring_progress_request = 17;
+    LedRingProgressResponse led_ring_progress_response = 18;
   }
 }
 
@@ -107,6 +110,28 @@ message EspNowUnicastTestResponse {
   uint32 seq = 2;
 }
 
+// Host → device: LED ring display (progress bar, digit, or clear).
+// mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10, same layout as firmware digit maps).
+message LedRingProgressRequest {
+  uint32 mode = 1;
+  /** 0–100: fraction of ring LEDs to light (mode=progress) */
+  uint32 progress = 2;
+  /** 0–10 (mode=digit) */
+  uint32 digit = 3;
+  uint32 r = 4;
+  uint32 g = 5;
+  uint32 b = 6;
+  /** 0–255 brightness scale applied to r/g/b */
+  uint32 intensity = 7;
+}
+
+message LedRingProgressResponse {
+  bool success = 1;
+  uint32 mode = 2;
+  uint32 progress = 3;
+  uint32 digit = 4;
+}
+
 // Host → device: begin UART OTA (erase inactive OTA slot; device replies OTA_STATUS).
 message OtaStartPayload {
   uint32 total_size = 1;