feat(ble): add BLE UART daemon notify API

tools/ble/ble_uart_bridge/docs/Quick-Start-BLE-UART-Daemon.md

@@ -114,6 +114,28 @@ Do not send requests to a daemon bound to a shared network interface unless that
 
 The CLI prints only the response payload. If the device returns a JSON object, the CLI prints it as JSON.
 
+## Send a notification from the CLI
+
+Use `daemon-notify` for fire-and-forget operations where the caller only needs the daemon to write to the BLE device and does not need a protocol response:
+
+```bash
+python main.py daemon-notify --op set_led --json '{"state": true}'
+```
+
+Send a raw string notification with the default operation name `raw`:
+
+```bash
+python main.py daemon-notify "hello"
+```
+
+Use a non-default daemon address:
+
+```bash
+python main.py daemon-notify --host 127.0.0.1 --port 8899 --op set_led --json '{"state": true}'
+```
+
+`daemon-notify` returns after the local BLE write completes. It does not wait for the device to send a JSONL response.
+
 ## HTTP API
 
 Daemon mode exposes a local HTTP API.
@@ -135,7 +157,7 @@ Response fields:
 | `is_connected` | Whether the BLE client is currently connected |
 | `pending_requests` | Number of pending request futures |
 | `single_flight` | Whether the daemon serializes requests |
-| `max_request_data_bytes` | Maximum JSON-encoded `data` size accepted by `/request` |
+| `max_request_data_bytes` | Maximum JSON-encoded `data` size accepted by `/request` and `/notify` |
 | `protocol` | Wire protocol name and version |
 
 ### `POST /request`
@@ -189,6 +211,54 @@ HTTP error behavior:
 | `502` | Device returned a protocol error or invalid response |
 | `504` | Timed out waiting for the device response |
 
+### `POST /notify`
+
+Sends one notification to the BLE device and returns without waiting for a protocol response:
+
+```bash
+curl -X POST http://127.0.0.1:8888/notify \
+  -H 'Content-Type: application/json' \
+  -d '{"op":"set_led","data":{"state":true}}'
+```
+
+Request body:
+
+```json
+{
+  "op": "set_led",
+  "data": {
+    "state": true
+  }
+}
+```
+
+Fields:
+
+| Field | Required | Meaning |
+| --- | --- | --- |
+| `op` | No | Operation name. Defaults to `raw`. |
+| `data` | Yes | Notification payload. Can be a string, number, boolean, array, object, or null. |
+
+Limits:
+
+- `op` must be 1 to 64 characters.
+- JSON-encoded `data` must not exceed 4096 bytes.
+
+Successful response:
+
+```json
+{
+  "ok": true
+}
+```
+
+HTTP error behavior:
+
+| HTTP status | Meaning |
+| --- | --- |
+| `413` | Request data exceeds the daemon payload limit |
+| `500` | Failed to send data to the BLE device |
+
 ## BLE JSONL RPC protocol
 
 The daemon communicates with the BLE device using newline-delimited JSON. Every message is one JSON object followed by `\n`.
@@ -226,7 +296,7 @@ Fields:
 | Field | Meaning |
 | --- | --- |
 | `v` | Protocol version. Current value is `1`. |
-| `id` | Request ID generated by the daemon. The device must echo this in the response. |
+| `id` | Request ID generated by the daemon. The device must echo this in `/request` responses. `/notify` uses an empty string because no response is expected. |
 | `op` | Operation name selected by the client. |
 | `data` | Request payload. |
 
@@ -295,7 +365,8 @@ On the BLE device, implement this loop conceptually:
 3. Parse each line as JSON.
 4. Read `id`, `op`, and `data`.
 5. Execute the requested operation.
-6. Send a JSON response with the same `id` and a final `\n`.
+6. If `id` is non-empty, send a JSON response with the same `id` and a final `\n`.
+7. If `id` is empty, treat the message as fire-and-forget and normally do not send a response.
 
 For example, an `echo` operation can return the same data:
 
@@ -303,6 +374,14 @@ For example, an `echo` operation can return the same data:
 {"v":1,"id":"6f8f...","ok":true,"data":"hello"}
 ```
 
+For notifications sent through `/notify`, the daemon uses an empty `id`:
+
+```json
+{"v":1,"id":"","op":"set_led","data":{"state":true}}
+```
+
+Firmware can execute the operation without responding. If it does respond with `id: ""`, the daemon will log the message as unsolicited because no pending request is waiting for that ID.
+
 ## Single-flight behavior
 
 The daemon currently processes one `/request` at a time. This is exposed as: