Adds a dedicated regression (tests/fix-2136-clock-local-today.test.cjs):
- realClock.localToday() returns the LOCAL calendar day under a pinned instant
+ TZ (America/Chicago → 2020-06-14, the issue's repro instant).
- realClock.today() is unchanged (UTC) — internal/cosmetic stamps stay UTC.
- localToday === today on a UTC host (no spurious divergence).
- makeFakeClock mirrors localToday (drop-in Clock substitute).
- field-level: a 'sync' transition with a split clock (today≠localToday)
writes the LOCAL day into Last Activity, proving the wiring uses localToday.
Mirrors localToday() in the fake clock helper and the inline fixedClock stubs
in state-transition.test.cjs / state-rebuild.test.cjs (the Clock interface now
requires it).
51b6e3c35c