fix(dify-builder): ground model on all model-bearing nodes, carry branch handles, clean test lint

Final consolidated fix wave from whole-branch review of the Real Build +
Edit Cognition slice:

- _ground now overwrites the model dict on ANY create_node whose config
  carries a model dict (llm, question-classifier, parameter-extractor),
  not just "llm", so a drifted/hallucinated provider/name on those other
  node types no longer flows through ungrounded.
- to_intents now carries a generator edge's sourceHandle/targetHandle
  into the connect intent's args (source_handle/target_handle) so
  branching nodes (if-else, question-classifier) wire onto the correct
  port instead of collapsing onto the default handle; edges without
  handles still produce bare {from_node, to_node} args.
- Cleared the 17 ruff errors (PT018/E302/E306/E501) across the slice's
  test files by splitting composite asserts, adding missing blank
  lines, and wrapping long lines -- no assertions weakened, no noqa.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

api/services/dify_builder/agent/graph_translate.py

@@ -45,9 +45,16 @@ def to_intents(graph: dict[str, Any]) -> list[MutationIntent]:
         src, tgt = edge.get("source"), edge.get("target")
         if not src or not tgt:
             continue
-        connects.append(MutationIntent(op="connect", args={
+        args: dict[str, Any] = {
             "from_node": remap.get(str(src), str(src)),
             "to_node": remap.get(str(tgt), str(tgt)),
-        }))
+        }
+        source_handle = edge.get("sourceHandle")
+        if source_handle:
+            args["source_handle"] = source_handle
+        target_handle = edge.get("targetHandle")
+        if target_handle:
+            args["target_handle"] = target_handle
+        connects.append(MutationIntent(op="connect", args=args))
 
     return creates + connects