test(app): add tuistory integration suite

[benvinegar]

Summary

• add an opt-in tuistory-backed integration test suite for the standalone app
• cover full PTY launch, cancel, save-to-file, and hotkey-driven UI behavior
• organize the new suite under packages/app/test/integration and wire test:integration scripts

Testing

• cd packages/app && bun run test:integration
• bun run typecheck

This PR description was generated by Pi using openai/gpt-5