fix(workflow): enforce domain state machine in dual validation path

validate_as_red/blue_lead now delegate to TestEntity. check_dual_validation routes through entity instead of assigning test.state directly. Side effects dispatched via domain events. Entity raises InvalidOperationError for backward compat. Removed 4 dead V1 xfail tests, fixed 2 real test issues. 224 passed, 0 xfailed.

backend/app/domain/test_entity.py

@@ -28,7 +28,11 @@ from dataclasses import dataclass, field
 from datetime import datetime
 from typing import Any
 
-from app.domain.errors import BusinessRuleViolation, InvalidStateTransition
+from app.domain.errors import (
+    BusinessRuleViolation,
+    InvalidOperationError,
+    InvalidStateTransition,
+)
 
 
 # ── Value objects ────────────────────────────────────────────────────
@@ -307,9 +311,22 @@ class TestEntity:
         self.paused_at = None
         return extra
 
+    def check_dual_validation(self) -> None:
+        """Evaluate both leads' votes and advance state if appropriate.
+
+        - Both **approved** -> ``validated``
+        - Either **rejected** -> ``rejected``
+        - Otherwise no change (waiting for the other lead).
+
+        Called automatically by :meth:`validate_red` and :meth:`validate_blue`.
+        Also available as a standalone entry point for backward compatibility
+        when validation fields are set externally.
+        """
+        self._check_dual_validation()
+
     def _assert_in_review(self, side: str) -> None:
         if self.state != TestState.in_review:
-            raise BusinessRuleViolation(
+            raise InvalidOperationError(
                 f"Cannot validate {side} side while test is in "
                 f"'{self.state.value}' state (must be in_review)"
             )
@@ -317,7 +334,7 @@ class TestEntity:
     @staticmethod
     def _assert_valid_vote(status: str) -> None:
         if status not in ("approved", "rejected"):
-            raise BusinessRuleViolation(
+            raise InvalidOperationError(
                 "validation_status must be 'approved' or 'rejected'"
             )