feat: introduce /admin API for stack administration and operations (#4401)

# What does this PR do?

- Add new /admin API (v1alpha) for administrative operations including
provider management, health checks, version info, and route listing
- Implement using FastAPI routers following batches pattern with proper
request/response models
- Endpoints: /admin/providers, /admin/providers/{id},
/admin/inspect/routes, /admin/health, /admin/version
- Create admin module structure: models.py, api.py, fastapi_routes.py,
init.py
- Add AdminImpl in llama_stack/core combining provider and inspect
functionality
- Deprecate standalone /providers and /inspect APIs (remain functional
for backward compatibility)
- Consolidate duplicate types: ProviderInfo, HealthInfo, RouteInfo, etc.
now defined once in admin.models

## Test Plan

new admin integration suite, uses generated stainless SDK, and records
new tests on this PR.

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

tests/integration/admin/__init__.py

@@ -0,0 +1,5 @@
+# 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.

tests/integration/admin/test_admin.py

@@ -0,0 +1,73 @@
+# 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.
+
+from llama_stack_client import LlamaStackClient
+
+from llama_stack.core.library_client import LlamaStackAsLibraryClient
+
+
+class TestAdmin:
+    def test_admin_providers_list(self, llama_stack_client: LlamaStackAsLibraryClient | LlamaStackClient):
+        provider_list = llama_stack_client.alpha.admin.list_providers()
+        assert provider_list is not None
+        assert len(provider_list) > 0
+
+        for provider in provider_list:
+            pid = provider.provider_id
+            provider = llama_stack_client.alpha.admin.inspect_provider(pid)
+            assert provider is not None
+
+    def test_health(self, llama_stack_client: LlamaStackAsLibraryClient | LlamaStackClient):
+        health = llama_stack_client.alpha.admin.health()
+        assert health is not None
+        assert health.status == "OK"
+
+    def test_version(self, llama_stack_client: LlamaStackAsLibraryClient | LlamaStackClient):
+        version = llama_stack_client.alpha.admin.version()
+        assert version is not None
+        assert version.version is not None
+
+    def test_list_routes_default(self, llama_stack_client: LlamaStackAsLibraryClient | LlamaStackClient):
+        """Test list_routes with default filter (non-deprecated v1 routes)."""
+        routes = llama_stack_client.alpha.admin.list_routes()
+        assert routes is not None
+        assert len(routes) > 0
+
+        # All routes should be non-deprecated
+        # Check that we don't see any /openai/ routes (which are deprecated)
+        openai_routes = [r for r in routes if "/openai/" in r.route]
+        assert len(openai_routes) == 0, "Default filter should not include deprecated /openai/ routes"
+
+        # Should see standard v1 routes like /inspect/routes, /health, /version
+        paths = [r.route for r in routes]
+        assert "/inspect/routes" in paths or "/v1/inspect/routes" in paths
+        assert "/health" in paths or "/v1/health" in paths
+
+    def test_list_routes_filter_by_deprecated(self, llama_stack_client: LlamaStackAsLibraryClient | LlamaStackClient):
+        """Test list_routes with deprecated filter."""
+        routes = llama_stack_client.alpha.admin.list_routes(api_filter="deprecated")
+        assert routes is not None
+
+        # When filtering for deprecated, we should get deprecated routes
+        # Verify we get some deprecated routes (e.g., /toolgroups, /shields, /models, etc.)
+        assert len(routes) > 0, "Deprecated filter should return some deprecated routes"
+
+    def test_list_routes_filter_by_v1(self, llama_stack_client: LlamaStackAsLibraryClient | LlamaStackClient):
+        """Test list_routes with v1 filter."""
+        routes = llama_stack_client.alpha.admin.list_routes(api_filter="v1")
+        assert routes is not None
+        assert len(routes) > 0
+
+        # Should not include deprecated routes
+        openai_routes = [r for r in routes if "/openai/" in r.route]
+        assert len(openai_routes) == 0
+
+        # Should include v1 routes
+        paths = [r.route for r in routes]
+        assert any(
+            "/v1/" in p or p.startswith("/inspect/") or p.startswith("/health") or p.startswith("/version")
+            for p in paths
+        )