The loop-recovery helper's notice (/run/fly/wd/recovery-notice.json,
FLY_RECOVERY_NOTICE) is served by serve.mjs at /recovery-notice.json and
polled once a second by the page, independent of flysim. Countdown shows a
Game Boy text box over the bottom of the game; acting covers the game while
flysim is down; done/failed show briefly. Stale, malformed or oversized
notices are ignored and helper strings are clipped to a closed charset.
Adds ?recovery=, __stage.recovery(), the recovery-notice dev tool, unit
tests (model, poller, serve.mjs route) and an e2e spec.
