fix: add sqlite wal mode and timeout

[QueryPlanner]

What

Add WAL mode and connection timeout to SQLite for ADK sessions.

Why

Rapid Telegram messages trigger concurrent database access. When a turn is cancelled mid-flight, its database connection is not fully released before a new turn starts writing, causing a database is locked OperationalError.

How

• Update build_session_db_kwargs to inject connect_args={"timeout": 15} for SQLite connections
• Add a SQLAlchemy connect event listener in create_session_service that executes PRAGMA journal_mode=WAL and PRAGMA synchronous=NORMAL
• Update unit tests in test_adk_runtime.py to assert the new kwargs config

Tests

• Run uv run pytest tests/test_adk_runtime.py

[gemini-code-assist]

Code Review

This pull request configures SQLite connection settings for the ADK runtime, introducing a 15-second connection timeout and setting the journal_mode to WAL and synchronous to NORMAL upon connection. It also updates the corresponding unit tests. The reviewer recommended wrapping the SQLite cursor operations in a try...finally block to ensure proper resource cleanup in case of exceptions, and suggested enabling PRAGMA foreign_keys=ON to enforce referential integrity.

[gemini-code-assist]

To ensure proper resource cleanup even if an exception occurs during the execution of the PRAGMA statements, wrap the cursor operations in a try...finally block. Additionally, consider enabling PRAGMA foreign_keys=ON to enforce referential integrity constraints, keeping it consistent with how SQLite is configured in src/blacki/storage/sqlite.py.

Suggested change

	cursor = dbapi_connection.cursor()
	cursor.execute("PRAGMA journal_mode=WAL")
	cursor.execute("PRAGMA synchronous=NORMAL")
	cursor.close()
	cursor = dbapi_connection.cursor()
	try:
	cursor.execute("PRAGMA journal_mode=WAL")
	cursor.execute("PRAGMA synchronous=NORMAL")
	cursor.execute("PRAGMA foreign_keys=ON")
	finally:
	cursor.close()