v0.5.0

Added

• One-command adoption — check_errors.py --init [--target DIR]
  scaffolds errors.txt / rules.txt / notes.txt (never overwriting
  existing files), installs the commit-msg gate (backup-safe),
  health-checks the log, and runs the unit-test suite. Built-in
  minimal scaffolds kick in when only check_errors.py was copied.