Review finding on PR #83194 (egilewski): Install-Venv committed the venv
transaction as soon as the replacement had a working interpreter, deleting
the parked previous venv. Install-Dependencies is a separate later stage
(a separate process under the stage-per-process bootstrap) and every
dependency tier or the baseline-import gate can still fail after that
point - a failed update could still leave Hermes and the blocker probe
unusable with no rollback source.
Now:
- Install-Venv records the parked backup in venv.pending-backup instead
of deleting it, and excludes it from the venv.stale.* sweep.
- Install-Dependencies wraps the dependency tiers + baseline-import gate
in the transaction: Restore-VenvBackup on failure (parks the failed
replacement as venv.failed.*, renames the previous venv back), and
Complete-VenvTransaction only after the imports prove the replacement
usable.
- Source-contract regression tests for the boundary
(tests/test_install_ps1_venv_transaction_boundary.py).
aa5a960675