refactor: build structured-output GenerateParams via struct update

Replaces the per-field if-let cascade in the structured completion path
with a single struct-update expression. The cascade had to be extended
by hand for every request field and silently dropped stop_sequences and
provider_options, which the non-structured path already forwarded.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/apps/fabro-server/src/server/handler/completions.rs

@@ -139,25 +139,23 @@ async fn create_completion(
         let msg_id = Ulid::new().to_string();
 
         if let Some(schema) = req.schema {
-            // Structured output uses generate_object for JSON parsing logic
+            // Structured output uses generate_object for JSON parsing logic.
-            let mut params =
+            // tools/tool_choice are not forwarded: GenerateParams carries
-                GenerateParams::new(&request.model, std::sync::Arc::new(client.clone()))
+            // executable Arc<Tool>s, not wire ToolDefinitions, and
-                    .messages(request.messages);
+            // generate_object sets response_format from the schema itself.
-            if let Some(ref p) = request.provider {
+            let params = GenerateParams {
-                params = params.provider(p);
+                messages: Some(request.messages),
-            }
+                provider: request.provider,
-            if let Some(temp) = request.temperature {
+                temperature: request.temperature,
-                params = params.temperature(temp);
+                top_p: request.top_p,
-            }
+                max_tokens: request.max_tokens,
-            if let Some(max_tokens) = request.max_tokens {
+                stop_sequences: request.stop_sequences,
-                params = params.max_tokens(max_tokens);
+                reasoning_effort: request.reasoning_effort,
-            }
+                speed: request.speed,
-            if let Some(top_p) = request.top_p {
+                metadata: request.metadata,
-                params = params.top_p(top_p);
+                provider_options: request.provider_options,
-            }
+                ..GenerateParams::new(request.model, std::sync::Arc::new(client.clone()))
-            if let Some(reasoning_effort) = request.reasoning_effort {
+            };
-                params = params.reasoning_effort(reasoning_effort);
-            }
             match generate_object(params, schema).await {
                 Ok(result) => {
                     // `result.finish_reason` / `result.usage` resolve through

lib/apps/fabro-server/src/server/tests.rs

@@ -15431,7 +15431,7 @@ async fn create_completion_structured_output_forwards_reasoning_effort() {
     let response = app.oneshot(req).await.unwrap();
     let body = response_json!(response, StatusCode::OK).await;
     assert_eq!(body["output"], json!({"answer": 42}));
-    completion.assert_calls(1);
+    completion.assert();
 }
 
 #[tokio::test]