Surgical reapply of PR #87878 (@kshitijk4poor's salvage of #87327 by
@liruixinch) onto current main — the receipt-boundary and summary
changes from this session made the original commits conflict.
- ZIP fallback now keys on git ACTUALLY having failed
(_should_zip_fallback_on_update_error): a dependency-install failure
after a successful pull can't be fixed by re-downloading source and
would clobber the tree (#87331 cascade trigger, #87304).
- _abort_zip_update_if_dirty_tree: refuse to overlay a dirty checkout
(-uall so user gitconfig can't blind the guard) + pre-swap TOCTOU
re-check with our own staging artifacts filtered (#91962, #87304).
- Failure-stage naming (_format_update_failure_stage) + stderr tail so
'Git update failed' stops mislabeling pip/uv failures.
- Receipt finalize preserved on the no-fallback failure path.
Co-authored-by: kshitijk4poor <82637225+kshitijk4poor@users.noreply.github.com>
Co-authored-by: liruixinch <liruixinch@outlook.com>
kshitijk4poor