v0.5.0

• Hardened git mechanics: merge commits in an absorb range are never
  flattened, diffs regenerate after every commit, mid-rebase and mid-merge
  states refuse cleanly, binary files stay whole, rename pairs stay together,
  empty stages stop the run, pre-staged files count as a grouping hint.
• Run options: --scope, --gate, --dry-run, with [run] and [protect]
  config in .preen.toml and an allow-no-verify standing-consent switch for
  hook-blocked repos.
• Undo guidance now uses git reset --keep so work done after a run survives.
• Timestamp spacing constraints: monotonic, never future, never before base.
• New banner and logo.