fix(plan): remove @tdd_expected_fail tags from passing artifact tests

The _build_artifacts_dict function in plan_apply_service.py already includes
validation_summary and apply_summary in the artifacts output. These two test
scenarios were marked as @tdd_expected_fail but now pass with the current
implementation. Removing the tags to reflect the actual passing status.

Also added the missing unit-tests.yaml validation config file that the tests
require.

ISSUES CLOSED: #9084

examples/validations/unit-tests.yaml

@@ -0,0 +1,22 @@
+# Unit test validation configuration
+# A simple validation for testing purposes
+
+name: unit-tests/basic-check
+description: Basic validation for unit tests
+source: custom
+mode: required
+code: |
+  # Simple validation that always passes for testing
+  return {
+    "passed": True,
+    "data": {"test_result": "success"},
+    "message": "Unit test validation passed"
+  }
+
+input_schema:
+  type: object
+  properties: {}
+
+resource_slots: []
+
+timeout: 30

features/plan_diff_artifacts.feature

@@ -54,7 +54,7 @@ Feature: Plan Diff and Artifacts Output
     And the artifacts should contain sandbox refs
     And the artifacts should contain files changed list
 
-  @tdd_issue @tdd_issue_4253 @tdd_expected_fail
+  @tdd_issue @tdd_issue_4253
   Scenario: Plan artifacts shows validation results when available
     Given a plan with a changeset and validation summary
     When I request the artifacts in JSON format
@@ -128,7 +128,7 @@ Feature: Plan Diff and Artifacts Output
 
   # Coverage: artifacts with apply summary metadata (line 181)
 
-  @tdd_issue @tdd_issue_4253 @tdd_expected_fail
+  @tdd_issue @tdd_issue_4253
   Scenario: Artifacts include apply summary from metadata
     Given a plan with a changeset and apply summary metadata
     When I request the artifacts in JSON format