feat(ack): bind test env to deployer and add regression mode

ACK 0.19.0 hands test-environment deploys to the deployer skill,
documents bug-fix as a first-class scenario, and adds
docs/ack/regression.yaml harvest plus a /ack regression run.

tests/test_ack_delivery.py

@@ -314,7 +314,7 @@ class AckDeliveryValidationTests(unittest.TestCase):
 
         self.assertEqual(validate_delivery.validate_builtin(contract), [])
 
-    def test_intents_must_point_at_matching_stop_points(self) -> None:
+    def test_test_environment_intent_requires_deployer_binding(self) -> None:
         contract = valid_contract()
         contract["intents"] = {
             "testEnvironment": "review",
@@ -323,33 +323,32 @@ class AckDeliveryValidationTests(unittest.TestCase):
 
         errors = validate_delivery.validate_builtin(contract)
         self.assertTrue(
-            any("intents.testEnvironment" in item and "validation_ready" in item for item in errors)
+            any("已改为 deployer 绑定" in item for item in errors)
         )
 
-        contract["intents"]["testEnvironment"] = "local-validation"
-        contract["profiles"]["local-validation"] = {
-            "stopAt": "validation_ready",
-            "steps": [
-                {"id": "build-local", "action": "build", "artifact": "service-deb"},
-                {
-                    "id": "deploy-local",
-                    "action": "deploy",
-                    "artifact": "service-deb",
-                    "environment": "test-server",
-                },
-                {
-                    "id": "health-local",
-                    "action": "health-check",
-                    "environment": "test-server",
-                },
-            ],
-        }
+        contract["intents"]["testEnvironment"] = {"via": "deployer", "env": "test"}
         self.assertEqual(validate_delivery.validate_builtin(contract), [])
 
         contract["intents"]["release"] = "missing-release"
         errors = validate_delivery.validate_builtin(contract)
         self.assertTrue(any("未定义 profile 'missing-release'" in item for item in errors))
 
+    def test_test_environment_binding_requires_deployer_env_directory(self) -> None:
+        contract = valid_contract()
+        contract["intents"] = {
+            "testEnvironment": {"via": "deployer", "env": "test"},
+            "release": None,
+        }
+        with tempfile.TemporaryDirectory() as temp_dir:
+            root = Path(temp_dir)
+            errors = validate_delivery.validate_builtin(contract, root)
+            self.assertTrue(
+                any(".skiff/deployer/test" in item for item in errors)
+            )
+            env_dir = root / ".skiff" / "deployer" / "test"
+            env_dir.mkdir(parents=True)
+            self.assertEqual(validate_delivery.validate_builtin(contract, root), [])
+
 
 if __name__ == "__main__":
     unittest.main()