loadbearer v0.2.1

• loadbearer --version / -V now report a full build version: the crate
  version plus the git commit, build date, target triple and profile, e.g.
  loadbearer 0.2.1 (a1b2c3d4e 2026-08-28, x86_64-pc-windows-msvc, release).
  A build.rs captures this at compile time; it honours SOURCE_DATE_EPOCH
  for reproducible builds and falls back to unknown for the commit when built
  outside a git checkout.

Full Changelog: v0.2.0...v0.2.1