Add <break-timer> tray: pick a duration, Start break pauses the session
clock (reusing clock.pause/resume), End break resumes it — so meal/comfort
break time is excluded from elapsed and drift stays honest. The shell owns
pause/resume + persistence (break store key); the rail shows a on-break
badge and gains a coffee chip. fmtCountdown (M:SS) added to format.js.
tests/components/break-timer.test.js + gm-shell-break.test.js (incl. the
30-play/20-break/10-play drift-honesty case) + fmtCountdown. 159 tests pass.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
