Start tracking a version number and a player-facing changelog, surfaced from
the ☰ menu via a new About item.
- frontend/src/lib/changelog.js: VERSION (bump every commit) + CHANGELOG.
- AboutModal.svelte: shows the version and changelog using the shared modal CSS;
closes via ×, backdrop click, or Escape.
- CornerMenu.svelte: new 'ℹ️ About' menu item, modal rendered outside the menu's
stacking context so it overlays correctly on every page.
- AGENTS.md: documents the bump-every-commit / log-only-user-facing convention.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
