v0.6.1

Added

• Bats unit tests + kcov coverage. A test/ suite asserts the bash scripts'
  pure functions — effect-arg building, load_config defaulting, logo
  resolution/picking, toggle state, the kill-debounce (#4), battery gating, and
  mirror-mode argument assembly. Both bin scripts now guard main "$@" so they
  can be sourced for testing. A new CI job runs the suite under kcov and
  uploads line coverage to Codecov; make unit and make coverage run it
  locally (both skip with a hint when the tool is missing, same as the linters).

Changed

• Security and dev docs refreshed. SECURITY.md now lists 0.6.x as
  supported (was 0.3.x) and documents the CI gates that guard the codebase.
  TESTING.md and LINTING.md cover the new unit suite and the coverage job.