fix(test/worker): assert on envelope-wrapped result shape (#7154)

worker_node was refactored to wrap task results in a {status, message,
data} envelope. Two tests asserted on the unwrapped shape:
  test_llm_chat_completion_success — expected `result["response"]`
  test_kb_search_success — expected `result["results"]`

With the Redis mock now actually applied (post-#6987 src.* fix), these
failures became visible. They had been silently passing on
stale-mock-luck during the entire src.* bug window.

Fix: update both tests to drill through `result["data"]` to the
canonical position. Add inline reference to #7154 explaining the shape.

Audit (per AC): traced execute_task → task_executor.execute → handlers.
Envelope is applied PER-HANDLER (consistent for task results). The
unwrapped helper-method returns at worker_node.py:104 / 206 / 215 etc.
are internal helpers, not user-facing task results — no drift surface
to file as a follow-up.

Acceptance criteria met:
- ✅ Both tests updated to assert on `result["data"]["response"]` /
     `result["data"]["results"]` — verified by 2/2 pass
- ✅ Envelope-pattern audit complete: handlers wrap consistently;
     helper-method returns are internal-only

Closes #7154

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: t

autobot-backend/worker_node_test.py

@@ -117,8 +117,11 @@ async def test_llm_chat_completion_success(self, worker_node):
 
         result = await worker_node.execute_task(task_payload)
 
+        # #7154: worker_node now wraps every response in a {status, message,
+        # data} envelope. The actual response sits at result["data"]["response"].
         assert result["status"] == "success"
-        assert "response" in result
+        assert "data" in result
+        assert "response" in result["data"]
         worker_node.llm_interface.chat_completion.assert_called_once()
         worker_node.security_layer.audit_log.assert_called()
 
@@ -137,8 +140,10 @@ async def test_kb_search_success(self, worker_node):
 
         result = await worker_node.execute_task(task_payload)
 
+        # #7154: worker_node envelope — actual results at result["data"]["results"].
         assert result["status"] == "success"
-        assert "results" in result
+        assert "data" in result
+        assert "results" in result["data"]
         worker_node.knowledge_base.search.assert_called_once_with("test query", 5)
 
     @pytest.mark.asyncio