fix(runtime): fail closed on offline artifact misses

tests/test_session_recording.py

@@ -15,6 +15,7 @@ import pytest
 import k1link.sessions.recording as recording_module
 from k1link.artifact_gateway import (
     ArtifactGateway,
+    ArtifactStoreUnavailable,
     CentralArtifactStore,
     LocalArtifactCache,
 )
@@ -184,7 +185,7 @@ def test_materializer_restores_exact_central_recording_without_export(
     assert exporter.calls == 0
 
 
-def test_default_recording_cache_has_no_application_byte_quota(
+def test_default_recording_cache_has_a_bounded_application_quota(
     tmp_path: Path,
     monkeypatch: pytest.MonkeyPatch,
 ) -> None:
@@ -195,7 +196,42 @@ def test_default_recording_cache_has_no_application_byte_quota(
         exporter=FakeExporter(),
     )
 
-    assert materializer.cache_max_bytes is None
+    assert materializer.cache_max_bytes == 8 * 1024 * 1024 * 1024
+
+
+def test_materializer_does_not_rebuild_when_central_store_is_offline(
+    tmp_path: Path,
+) -> None:
+    command = _command(tmp_path / "source")
+    exporter = FakeExporter()
+
+    class OfflineGateway:
+        def resolve_role(
+            self,
+            namespace: str,
+            key: str,
+            role: str,
+        ) -> object:
+            assert (namespace, key, role) == (
+                "sessions",
+                command.session_id,
+                "base-rrd",
+            )
+            raise ArtifactStoreUnavailable("offline cache miss")
+
+    materializer = SessionRecordingMaterializer(
+        tmp_path / "private",
+        exporter=exporter,
+        artifact_gateway=OfflineGateway(),  # type: ignore[arg-type]
+    )
+
+    with pytest.raises(
+        RecordingMaterializationError,
+        match="not present in the local artifact cache",
+    ):
+        materializer.materialize(command)
+
+    assert exporter.calls == 0
 
 
 def test_delete_cached_refuses_a_live_lease_then_removes_the_exact_cache(