Change chat/update from notification to request

State-modifying operations that persist to DB should use request
semantics so the client gets acknowledgment. This aligns chat/update
with chat/clear, chat/delete, chat/fork, etc.

- Use receive-request + eventually instead of receive-notification
- Return {} from update-chat (consistent with other chat operations)
- Update protocol docs to reflect request semantics

🤖 Generated with [eca](https://eca.dev)

Co-Authored-By: eca <git@eca.dev>

Author: ericdallo

docs/protocol.md

@@ -1707,12 +1707,12 @@ _Response:_
 interface ChatDeleteResponse {}
 ```
 
-### Chat update (➡️)
+### Chat update (↩️)
 
-A client notification to update chat metadata like title.
-Server will broadcast the change to all connected clients via `chat/contentReceived` with metadata content.
+A client request to update chat metadata like title.
+Server will persist the change, broadcast to all connected clients via `chat/contentReceived` with metadata content, and return an empty response.
 
-_Notification:_
+_Request:_
 
 * method: `chat/update`
 * params: `ChatUpdateParams` defined as follows:
@@ -1731,6 +1731,12 @@ interface ChatUpdateParams {
 }
 ```
 
+_Response:_
+
+```typescript
+interface ChatUpdateResponse {}
+```
+
 ### Chat selected agent changed (➡️)
 
 A client notification for server telling the user selected a different agent in chat.

src/eca/features/chat.clj

@@ -1153,7 +1153,8 @@
                                      {:chat-id chat-id
                                       :role    "system"
                                       :content {:type :metadata :title title}})
-    (db/update-workspaces-cache! @db* metrics)))
+    (db/update-workspaces-cache! @db* metrics))
+  {})
 
 (defn rollback-chat
   "Remove messages from chat in db until content-id matches.

src/eca/server.clj

@@ -115,8 +115,8 @@
 (defmethod jsonrpc.server/receive-request "chat/fork" [_ components params]
   (eventually (handlers/chat-fork (with-config components) params)))
 
-(defmethod jsonrpc.server/receive-notification "chat/update" [_ components params]
-  (async-notify (handlers/chat-update (with-config components) params)))
+(defmethod jsonrpc.server/receive-request "chat/update" [_ components params]
+  (eventually (handlers/chat-update (with-config components) params)))
 
 (defmethod jsonrpc.server/receive-notification "mcp/stopServer" [_ components params]
   (async-notify (handlers/mcp-stop-server (with-config components) params)))