refactor: enforce top-level imports for llama-stack-api

Enforce that all imports from llama-stack-api use the form:

from llama_stack_api import <symbol>

 This prevents external code from accessing internal package structure
 (e.g., llama_stack_api.agents, llama_stack_api.common.*) and establishes
 a clear public API boundary.

 Changes:
 - Export 400+ symbols from llama_stack_api/__init__.py
 - Include all API types, common utilities, and strong_typing helpers
 - Update files across src/llama_stack, docs/, tests/, scripts/
 - Convert all submodule imports to top-level imports
 - ensure docs use the proper importing structure

 Addresses PR review feedback requiring explicit __all__ definition to
 prevent "peeking inside" the API package.

Signed-off-by: Charlie Doern <cdoern@redhat.com>

tests/unit/server/test_access_control.py

@@ -8,8 +8,7 @@ from unittest.mock import MagicMock, Mock, patch
 
 import pytest
 import yaml
-from llama_stack_api.datatypes import Api
-from llama_stack_api.models import ModelType
+from llama_stack_api import Api, ModelType
 from pydantic import TypeAdapter, ValidationError
 
 from llama_stack.core.access_control.access_control import AccessDeniedError, is_action_allowed

tests/unit/server/test_auth.py

@@ -144,7 +144,7 @@ def middleware_with_mocks(mock_auth_endpoint):
     middleware = AuthenticationMiddleware(mock_app, auth_config, {})
 
     # Mock the route_impls to simulate finding routes with required scopes
-    from llama_stack_api.schema_utils import WebMethod
+    from llama_stack_api import WebMethod
 
     routes = {
         ("POST", "/test/scoped"): WebMethod(route="/test/scoped", method="POST", required_scope="test.read"),

tests/unit/server/test_resolver.py

@@ -9,8 +9,7 @@ import sys
 from typing import Any, Protocol
 from unittest.mock import AsyncMock, MagicMock
 
-from llama_stack_api.datatypes import InlineProviderSpec, ProviderSpec
-from llama_stack_api.inference import Inference
+from llama_stack_api import Inference, InlineProviderSpec, ProviderSpec
 from pydantic import BaseModel, Field
 
 from llama_stack.core.datatypes import Api, Provider, StackRunConfig

tests/unit/server/test_sse.py

@@ -9,7 +9,7 @@ import logging  # allow-direct-logging
 from unittest.mock import AsyncMock, MagicMock
 
 import pytest
-from llama_stack_api.common.responses import PaginatedResponse
+from llama_stack_api import PaginatedResponse
 
 from llama_stack.core.server.server import create_dynamic_typed_route, create_sse_event, sse_generator