User can now pick any owned game by Steam app_id via `pick-manual <id>`.
The script resolves the game name, asks for YES confirmation, then locks
all other commands for 14 days or until the game is 100% complete.
Post-assignment steps (uninstall others, install, hide library) mirror
the automatic pick flow. Lock is checked before every command including
add-exception. Also fixes pre-existing test failures in hltb, stats,
and web_dataset modules and adds 100% coverage for all changed code.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>