Add BLE host transport selectable via DIP8 alongside UART.

Master can speak the same framed protobuf protocol over NimBLE or UART; goTool gains -ble, ble-rtt, and ble-stream timing checks for ESP-NOW coexistence.

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

main/ble_host.h

@@ -0,0 +1,22 @@
+#ifndef BLE_HOST_H
+#define BLE_HOST_H
+
+#include "esp_err.h"
+#include "freertos/FreeRTOS.h"
+#include "freertos/queue.h"
+#include <stddef.h>
+#include <stdint.h>
+
+/** Start NimBLE host transport (Master only). Uses same framing as UART. */
+esp_err_t init_ble_host(QueueHandle_t cmd_queue);
+
+/** True when a central is connected and CCCD notify is enabled. */
+bool ble_host_ready(void);
+
+/** Negotiated ATT MTU (default 23 until exchange). */
+uint16_t ble_host_att_mtu(void);
+
+/** Max notify/write payload bytes (ATT MTU - 3). */
+uint16_t ble_host_max_payload(void);
+
+#endif