Previously the database path depended on app.getPath('userData') which
varies with app name changes (CodePilot vs codepilot vs Claude GUI).
Now uses a fixed ~/.codepilot/ directory for both dev and production.
Includes automatic migration: on first launch, if the DB doesn't exist
at the new path, it checks old locations (Application Support variants
and the old dev-mode data/ folder) and copies the database over.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>