feat: add adk folder manager and per agent local storage helpers

Creates AdkFolderManager for creating/resetting the .adk layout, helper builders that return SQLite- and filesystembacked services for each agent

Co-authored-by: George Weale <gweale@google.com>
PiperOrigin-RevId: 831206377

tests/unittests/cli/utils/test_dot_adk_folder.py

@@ -0,0 +1,47 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import annotations
+
+from pathlib import Path
+
+from google.adk.cli.utils.dot_adk_folder import dot_adk_folder_for_agent
+from google.adk.cli.utils.dot_adk_folder import DotAdkFolder
+import pytest
+
+
+def test_paths_are_relative_to_agent_dir(tmp_path: Path):
+  agent_dir = tmp_path / "agent_a"
+  folder = DotAdkFolder(agent_dir)
+
+  assert folder.dot_adk_dir == agent_dir.resolve() / ".adk"
+  assert folder.artifacts_dir == folder.dot_adk_dir / "artifacts"
+  assert folder.session_db_path == folder.dot_adk_dir / "session.db"
+
+
+def test_for_agent_validates_app_name(tmp_path: Path):
+  agents_root = tmp_path / "agents"
+  agents_root.mkdir()
+
+  with pytest.raises(ValueError):
+    dot_adk_folder_for_agent(
+        agents_root=agents_root, app_name="../escape_attempt"
+    )
+
+  folder = dot_adk_folder_for_agent(
+      agents_root=agents_root, app_name="valid_agent"
+  )
+
+  expected_dir = (agents_root / "valid_agent").resolve()
+  assert folder.agent_dir == expected_dir