feat!: providers use unified 'persistence' field

BREAKING CHANGE: Provider config field names changed for semantic clarity

- Rename kvstore → persistence for all providers
- Simple providers: flat persistence with backend reference
- Complex providers (agents): nested persistence.agent_state + persistence.responses
- Files provider: metadata_store → persistence
- Provider configs now clearly express 'how do I persist?' not 'what type of store?'

Example:
  # Before
  config:
    kvstore:
      backend: kvstore
      namespace: faiss

  # After
  config:
    persistence:
      backend: kvstore
      namespace: faiss

  # Agents (nested)
  config:
    persistence:
      agent_state:
        backend: kvstore
        namespace: agents
      responses:
        backend: sqlstore
        namespace: responses

llama_stack/providers/remote/vector_io/weaviate/config.py

@@ -19,7 +19,7 @@ from llama_stack.schema_utils import json_schema_type
 class WeaviateVectorIOConfig(BaseModel):
     weaviate_api_key: str | None = Field(description="The API key for the Weaviate instance", default=None)
     weaviate_cluster_url: str | None = Field(description="The URL of the Weaviate cluster", default="localhost:8080")
-    kvstore: KVStoreConfig | None = Field(description="Config for KV store backend (SQLite only for now)", default=None)
+    persistence: KVStoreConfig | None = Field(description="Config for KV store backend (SQLite only for now)", default=None)
 
     @classmethod
     def sample_run_config(
@@ -30,7 +30,7 @@ class WeaviateVectorIOConfig(BaseModel):
         return {
             "weaviate_api_key": None,
             "weaviate_cluster_url": "${env.WEAVIATE_CLUSTER_URL:=localhost:8080}",
-            "kvstore": SqliteKVStoreConfig.sample_run_config(
+            "persistence": SqliteKVStoreConfig.sample_run_config(
                 __distro_dir__=__distro_dir__,
                 db_name="weaviate_registry.db",
             ),

llama_stack/providers/remote/vector_io/weaviate/weaviate.py

@@ -318,8 +318,8 @@ class WeaviateVectorIOAdapter(
     async def initialize(self) -> None:
         """Set up KV store and load existing vector DBs and OpenAI vector stores."""
         # Initialize KV store for metadata if configured
-        if self.config.kvstore is not None:
-            self.kvstore = await kvstore_impl(self.config.kvstore)
+        if self.config.persistence is not None:
+            self.kvstore = await kvstore_impl(self.config.persistence)
         else:
             self.kvstore = None
             log.info("No kvstore configured, registry will not persist across restarts")