- Create a disposable HOME/USERPROFILE env for scripts/test-changed.mjs execution
- Run isolation guard checks with the same isolated env, including cache-hit no-op paths
- Clean up temp HOME after test execution to avoid residue
- Update test coverage and contributing docs for the shared isolation behavior
Fusion-Task-Id: FN-3610
This merge lands five FN-3593 commits establishing a test isolation contract with a new `scripts/check-test-isolation.mjs` guard that scans for accidental `beforeEach`/`afterEach`/`beforeAll`/`afterAll` in setup helpers, plus per-package `setup-test-isolation.ts` bootstraps that canonicalize the pat
Fusion-Task-Id: FN-3593