Add focused tests for persistence config and resolver

Tests cover critical failure modes:
- Backend reference validation catches config errors
- Namespace overlay logic for KVStore isolation
- Type safety: inference requires SqlStore
- Queue parameter preservation
- Integration with real distribution configs

tests/integration/test_persistence_integration.py

@@ -0,0 +1,67 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+import yaml
+
+from llama_stack.core.datatypes import StackRunConfig
+from llama_stack.core.persistence_resolver import (
+    resolve_inference_store_config,
+    resolve_metadata_store_config,
+)
+from llama_stack.providers.utils.kvstore.config import SqliteKVStoreConfig
+from llama_stack.providers.utils.sqlstore.sqlstore import (
+    PostgresSqlStoreConfig,
+    SqliteSqlStoreConfig,
+)
+
+
+def test_starter_distribution_config_loads_and_resolves():
+    """Integration: Actual starter config should parse and resolve all stores."""
+    with open("llama_stack/distributions/starter/run.yaml") as f:
+        config_dict = yaml.safe_load(f)
+
+    config = StackRunConfig(**config_dict)
+
+    # Config should have persistence with default backend
+    assert config.persistence is not None
+    assert "default" in config.persistence.backends
+    assert isinstance(config.persistence.backends["default"], SqliteSqlStoreConfig)
+
+    # Stores should reference the default backend
+    assert config.persistence.stores is not None
+    assert config.persistence.stores.metadata.backend == "default"
+    assert config.persistence.stores.inference.backend == "default"
+
+    # Resolution should work
+    metadata_store = resolve_metadata_store_config(config.persistence, "starter")
+    assert isinstance(metadata_store, SqliteKVStoreConfig)
+
+    sql_config, max_queue, num_writers = resolve_inference_store_config(config.persistence)
+    assert isinstance(sql_config, SqliteSqlStoreConfig)
+    assert max_queue > 0
+    assert num_writers > 0
+
+
+def test_postgres_demo_distribution_config_loads():
+    """Integration: Postgres demo should use Postgres backend for all stores."""
+    with open("llama_stack/distributions/postgres-demo/run.yaml") as f:
+        config_dict = yaml.safe_load(f)
+
+    config = StackRunConfig(**config_dict)
+
+    # Should have postgres backend
+    assert config.persistence is not None
+    assert "default" in config.persistence.backends
+    assert isinstance(config.persistence.backends["default"], PostgresSqlStoreConfig)
+
+    # Both stores use same postgres backend
+    assert config.persistence.stores.metadata.backend == "default"
+    assert config.persistence.stores.inference.backend == "default"
+
+    # Resolution returns postgres config
+    sql_config, _, _ = resolve_inference_store_config(config.persistence)
+    assert isinstance(sql_config, PostgresSqlStoreConfig)
+    assert sql_config.host == "${env.POSTGRES_HOST:=localhost}"