dirs::config_dir() and dirs::data_dir() both return ~/Library/Application Support
on macOS, so data_dir == config parent dir. ResetScope::DataOnly removes data_dir
and silently deletes config.toml along with it.
Fix: bypass dirs crate fallback for config/data/cache dirs; use
$HOME/.config, $HOME/.local/share, $HOME/.cache directly (XDG standard).
xdg_state_dir already used this pattern. dirs::home_dir() still used for
portability.
Migration: Config::load(None) auto-copies legacy ~/Library/Application
Support/kebab/config.toml to the new ~/.config/kebab/ on first run and
prints a migration notice to stderr.
