Lift line coverage back over the 95% floor after the Flutter 3.44.1
merge nudged it to 94.99%. Adds tests for the changeWord/no-op-edit/
empty-paste/word-motion-edge branches in vim_edit_ops, the lone-key
flush path in SequenceMatcher, and the keybindings-ui / vim extension
identity + deactivate paths.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>