Hermes-Setup.exe replaced install.ps1's .hermes-bootstrap-complete with its
own copy: completedAtUnix instead of the completedAt every other writer and
reader uses (install.ps1, Electron main, hermes_cli/source_stamp.py,
scripts/verify-bootstrap-version-stamp.py), and a pinnedCommit from a bare
`git rev-parse HEAD`, which is null on a machine where git exists only as
the PM-staged binary install.ps1 uses.
The receipt now carries completedAt (UTC ISO-8601, milliseconds), and the
commit resolves like install.ps1's Stage-Complete: the pinned commit, else
the checkout HEAD read from its ref files (loose ref or packed-refs), else
the full sha install.ps1 already recorded (read BOM-tolerant).
Fixes#124949
07be7d47ed