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/distributions/ci-tests/run.yaml

@@ -94,29 +94,29 @@ providers:
   - provider_id: faiss
     provider_type: inline::faiss
     config:
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: faiss
   - provider_id: sqlite-vec
     provider_type: inline::sqlite-vec
     config:
       db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/ci-tests}/sqlite_vec.db
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: sqlite_vec
   - provider_id: ${env.MILVUS_URL:+milvus}
     provider_type: inline::milvus
     config:
       db_path: ${env.MILVUS_DB_PATH:=~/.llama/distributions/ci-tests}/milvus.db
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: milvus
   - provider_id: ${env.CHROMADB_URL:+chromadb}
     provider_type: remote::chromadb
     config:
       url: ${env.CHROMADB_URL:=}
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: chromadb
   - provider_id: ${env.PGVECTOR_DB:+pgvector}
     provider_type: remote::pgvector
@@ -126,16 +126,16 @@ providers:
       db: ${env.PGVECTOR_DB:=}
       user: ${env.PGVECTOR_USER:=}
       password: ${env.PGVECTOR_PASSWORD:=}
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: pgvector
   files:
   - provider_id: meta-reference-files
     provider_type: inline::localfs
     config:
       storage_dir: ${env.FILES_STORAGE_DIR:=~/.llama/distributions/ci-tests/files}
-      metadata_store:
-        backend: default
+      persistence:
+        backend: sqlstore
         namespace: files
   safety:
   - provider_id: llama-guard
@@ -148,12 +148,13 @@ providers:
   - provider_id: meta-reference
     provider_type: inline::meta-reference
     config:
-      persistence_store:
-        backend: default
-        namespace: agents
-      responses_store:
-        backend: default
-        namespace: responses
+      persistence:
+        agent_state:
+          backend: kvstore
+          namespace: agents
+        responses:
+          backend: sqlstore
+          namespace: responses
   telemetry:
   - provider_id: meta-reference
     provider_type: inline::meta-reference
@@ -171,21 +172,21 @@ providers:
   - provider_id: meta-reference
     provider_type: inline::meta-reference
     config:
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: eval
   datasetio:
   - provider_id: huggingface
     provider_type: remote::huggingface
     config:
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: huggingface
   - provider_id: localfs
     provider_type: inline::localfs
     config:
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: localfs_datasetio
   scoring:
   - provider_id: basic
@@ -215,19 +216,22 @@ providers:
   - provider_id: reference
     provider_type: inline::reference
     config:
-      kvstore:
-        backend: default
+      persistence:
+        backend: kvstore
         namespace: batches
 persistence:
   backends:
-    default:
+    kvstore:
       type: sqlite
-      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/ci-tests}/store.db
+      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/ci-tests}/kvstore.db
+    sqlstore:
+      type: sqlite
+      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/ci-tests}/sqlstore.db
   stores:
     metadata:
-      backend: default
+      backend: kvstore
     inference:
-      backend: default
+      backend: sqlstore
 models: []
 shields:
 - shield_id: llama-guard

llama_stack/distributions/postgres-demo/run.yaml

@@ -73,7 +73,14 @@ providers:
     provider_type: remote::model-context-protocol
 persistence:
   backends:
-    default:
+    kvstore:
+      type: postgres
+      host: ${env.POSTGRES_HOST:=localhost}
+      port: ${env.POSTGRES_PORT:=5432}
+      db: ${env.POSTGRES_DB:=llamastack}
+      user: ${env.POSTGRES_USER:=llamastack}
+      password: ${env.POSTGRES_PASSWORD:=llamastack}
+    sqlstore:
       type: postgres
       host: ${env.POSTGRES_HOST:=localhost}
       port: ${env.POSTGRES_PORT:=5432}
@@ -82,9 +89,9 @@ persistence:
       password: ${env.POSTGRES_PASSWORD:=llamastack}
   stores:
     metadata:
-      backend: default
+      backend: kvstore
     inference:
-      backend: default
+      backend: sqlstore
 models:
 - metadata: {}
   model_id: ${env.INFERENCE_MODEL}

llama_stack/distributions/starter/run.yaml

@@ -220,14 +220,17 @@ providers:
         db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/starter}/batches.db
 persistence:
   backends:
-    default:
+    kvstore:
       type: sqlite
-      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/starter}/store.db
+      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/starter}/kvstore.db
+    sqlstore:
+      type: sqlite
+      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/starter}/sqlstore.db
   stores:
     metadata:
-      backend: default
+      backend: kvstore
     inference:
-      backend: default
+      backend: sqlstore
 models: []
 shields:
 - shield_id: llama-guard

llama_stack/distributions/watsonx/run.yaml

@@ -105,14 +105,17 @@ providers:
         db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/watsonx}/files_metadata.db
 persistence:
   backends:
-    default:
+    kvstore:
       type: sqlite
-      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/watsonx}/store.db
+      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/watsonx}/kvstore.db
+    sqlstore:
+      type: sqlite
+      db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/watsonx}/sqlstore.db
   stores:
     metadata:
-      backend: default
+      backend: kvstore
     inference:
-      backend: default
+      backend: sqlstore
 models:
 - metadata: {}
   model_id: meta-llama/llama-3-3-70b-instruct