Add node location access RPCs and operator visibility

docs/api/PROTOCOL.md

@@ -604,17 +604,22 @@ Register node role/capabilities for the current WebSocket connection.
 
 Return negotiated capabilities for the currently registered node connection.
 
-#### `system.capabilities`
+#### `node.location.set`
 
-Return gateway protocol version, node policy status, and feature-gate snapshot.
+Update the last-known location for the currently registered node connection.
+Requires `server.nodes.enabled: true` and `server.nodes.location.enabled: true`.
 
 **Request:**
 ```json
 {
-  "id": 8,
-  "method": "agent.cancel",
+  "id": 10,
+  "method": "node.location.set",
   "params": {
-    "sessionId": "telegram:123456"
+    "latitude": 37.7749,
+    "longitude": -122.4194,
+    "accuracyMeters": 12.4,
+    "source": "gps",
+    "capturedAt": 1763241200000
   }
 }
 ```
@@ -622,13 +627,63 @@ Return gateway protocol version, node policy status, and feature-gate snapshot.
 **Response:**
 ```json
 {
-  "id": 8,
+  "id": 10,
   "result": {
-    "cancelled": true
+    "updated": true,
+    "node": { "id": "companion-desktop", "role": "companion" },
+    "location": {
+      "latitude": 37.7749,
+      "longitude": -122.4194,
+      "accuracyMeters": 12.4,
+      "source": "gps",
+      "capturedAt": 1763241200000,
+      "receivedAt": 1763241200451
+    }
   }
 }
 ```
 
+#### `node.location.get`
+
+Return the stored last-known location for the currently registered node connection.
+
+#### `system.capabilities`
+
+Return gateway protocol version, node policy status, and feature-gate snapshot.
+
+**Request:**
+```json
+{
+  "id": 11,
+  "method": "system.capabilities"
+}
+```
+
+**Response:**
+```json
+{
+  "id": 11,
+  "result": {
+    "protocol": { "version": 1 },
+    "nodes": {
+      "enabled": true,
+      "locationEnabled": true,
+      "allowedRoles": ["companion"],
+      "registered": true,
+      "role": "companion",
+      "nodeId": "companion-desktop"
+    },
+    "featureGates": {
+      "ui.canvas": true
+    }
+  }
+}
+```
+
+#### `system.location`
+
+Return the operator-facing snapshot of registered node locations.
+
 #### `agent.setToolUseCallback`
 
 Set callback for tool use events (for confirmation UI).