Share canonicalize_location and resolve_existing_workflow_location
between the local package resolver and the version collector, drop the
redundant package-root pre-check and the PackageFileReadError enum in
favor of anyhow context, and read HEAD's SHA from git2 instead of a
separate rev-parse subprocess.
Make GitRunTargetObservation a plain struct, replace the repo-info
tuple with a named struct, tighten the closure view trait, avoid
deep-cloning the root workflow during collected validation, remove the
unused into_closure accessor, and dedupe test helpers.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>