## Problem
Review on #3151: with isCurrent reduced to store liveness, a completed
run's context stays current while a forced same-directory rerun starts,
so a late deferred response could commit over the newer run's state.
## Fix
Track a per-directory run sequence. isCurrent captures the sequence at
run start and stays true across settle (deferred recovery pulls still
commit — the original bug) but flips false the moment a newer run for
the same directory begins. Entries are cleared on directory disposal.
## Validation
- New test: after a forced rerun the first context is retired and the
second is current. 20 pass in child-store.test.ts.
- bun test src/sync/: 540 pass / 15 fail — same 15 pre-existing on main.
- type-check and oxlint clean on authored lines.
yangyaofei
02ab4136de