fix(agentHost): await dbClose to resolve flaky session database tests

[ruryu]

Summary

This PR fixes a flaky test issue in the SessionDatabase module (#306057). The root cause was an un-awaited db.close() call, which led to race conditions where a database file might still be locked when the next test case started.

Changes

• Database Lifecycle: Replaced db.close() with dbClose(db) in sessionDatabase.ts to ensure the asynchronous database closure is properly awaited.
• Type Mapping: Refactored SQLite row mapping to correctly handle null values from the database, ensuring they are accurately represented in TypeScript.
• Enable Test: Re-enabled the 'returns empty array when given empty array' test case which was previously skipped due to flakiness.

Verification

• Verified by running scripts/test.sh --grep "SessionDatabase" on WSL2 with Node v22.
• 30 tests passing consistently.
• Stress-tested the suite multiple times to ensure the race condition is resolved.

Fixes #306057

[ruryu]

@microsoft-github-policy-service agree

[Copilot]

Pull request overview

This PR addresses flakiness in SessionDatabase unit tests by ensuring the underlying SQLite connection is fully closed before subsequent tests run, avoiding file-lock race conditions in the agent host platform layer.

Changes:

• Await SQLite database closure by switching db.close() to the existing promise wrapper dbClose(db) in SessionDatabase.close().
• Re-enable the previously skipped regression test for getFileEdits([]) returning an empty array.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/vs/platform/agentHost/node/sessionDatabase.ts	Ensures close() truly awaits SQLite connection shutdown by using dbClose(db).
src/vs/platform/agentHost/test/node/sessionDatabase.test.ts	Re-enables the previously skipped flaky test case after the close race is addressed.