fix(api): allow canvas_type in agent create and update APIs (#15201)

### What problem does this PR solve?

Creating or updating an agent via `POST /api/v1/agents` and `PUT
/api/v1/agents/{agent_id}` did not persist `canvas_type` because the
handler `req` dict never assigned the field before
`UserCanvasService.save` / `update_by_id`.


### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)
- [ ] New Feature (non-breaking change which adds functionality)
- [ ] Documentation Update
- [ ] Refactoring
- [ ] Performance Improvement
- [ ] Other (please describe):

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

sdk/python/ragflow_sdk/ragflow.py

@@ -257,19 +257,35 @@ class RAGFlow:
             return Agent(self, res["data"])
         raise Exception(res["message"])
 
-    def create_agent(self, title: str, dsl: dict, description: str | None = None) -> None:
+    def create_agent(
+        self,
+        title: str,
+        dsl: dict,
+        description: str | None = None,
+        canvas_type: str | None = None,
+    ) -> None:
         req = {"title": title, "dsl": dsl}
 
         if description is not None:
             req["description"] = description
 
+        if canvas_type is not None:
+            req["canvas_type"] = canvas_type
+
         res = self.post("/agents", req)
         res = res.json()
 
         if res.get("code") != 0:
             raise Exception(res["message"])
 
-    def update_agent(self, agent_id: str, title: str | None = None, description: str | None = None, dsl: dict | None = None) -> None:
+    def update_agent(
+        self,
+        agent_id: str,
+        title: str | None = None,
+        description: str | None = None,
+        dsl: dict | None = None,
+        canvas_type: str | None = None,
+    ) -> None:
         req = {}
 
         if title is not None:
@@ -281,6 +297,9 @@ class RAGFlow:
         if dsl is not None:
             req["dsl"] = dsl
 
+        if canvas_type is not None:
+            req["canvas_type"] = canvas_type
+
         res = self.put(f"/agents/{agent_id}", req)
         res = res.json()