Two-part root cause (found by the lh-ui stream + master together): (1)
src/store/jobs.ts updateJob unconditionally overwrote updatedAt with now(),
silently clobbering any explicit patch timestamp — JobPatch types it as
patchable but the adapter ignored it, so order-sensitive tests rode on
same-millisecond tie-breaking (failed ~4/5 in isolation). The store now
honors patch.updatedAt ?? now() — semantics-preserving for every existing
caller, which never passed updatedAt explicitly. (2) the activity-feed
test's finally wiped the ENTIRE shared data/jobs dir — with node:test
running test files as concurrent processes, that deletes other processes'
live fixtures; cleanup is now scoped to the test's own created ids.