feat(registry): añade FileSystemPolicyStore con carga YAML versionada

Incluye 'yaml' en los overrides de mypy (PyYAML no trae type stubs).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/fixtures/policies/test_policy/index.yaml

@@ -0,0 +1,8 @@
+name: test_policy
+versions:
+  - id: v1
+    hash: deadbeef
+    author: pytest
+    message: fixture inicial
+    created_at: 2026-01-01T00:00:00Z
+active_version: v1

tests/fixtures/policies/test_policy/versions/v1.yaml

@@ -0,0 +1,13 @@
+name: test_policy
+version: v1
+description: Política de prueba
+input_validators:
+  - type: detect_pii
+    config:
+      entities: [PERSON, EMAIL]
+      severity_on_match: block
+output_validators:
+  - type: schema_match
+    config:
+      severity_on_mismatch: block
+on_validator_error: fail_closed

tests/unit/test_policy_store.py

@@ -0,0 +1,36 @@
+"""Tests del PolicyStore."""
+
+from pathlib import Path
+
+import pytest
+
+from agentforge_core.registry.policy_store import FileSystemPolicyStore
+
+FIXTURES = Path(__file__).parent.parent / "fixtures" / "policies"
+
+
+def test_list_policies() -> None:
+    store = FileSystemPolicyStore(FIXTURES)
+    names = [p.name for p in store.list_policies()]
+    assert "test_policy" in names
+
+
+def test_get_policy_devuelve_version_activa() -> None:
+    store = FileSystemPolicyStore(FIXTURES)
+    p = store.get_policy("test_policy")
+    assert p.version == "v1"
+    assert len(p.input_validators) == 1
+    assert p.input_validators[0].type == "detect_pii"
+
+
+def test_get_policy_inexistente_lanza_error() -> None:
+    store = FileSystemPolicyStore(FIXTURES)
+    with pytest.raises(FileNotFoundError):
+        store.get_policy("inexistente")
+
+
+def test_list_versions() -> None:
+    store = FileSystemPolicyStore(FIXTURES)
+    metas = store.list_versions("test_policy")
+    assert metas[0].id == "v1"
+    assert metas[0].author == "pytest"