Two places test for "a character the user typed" by hand, and a third
one is about to be needed. Give the test a name.
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
This changes not only how we store modifiers (inside of Key instead of passing
it separately), but also how we parse keybinding strings: it supports all
combinations of modifiers now (if the terminal supports it, that is).
This bundles the keyName and a rune, so that we don't have to pass these around
separately everywhere. This should make it easier to swap out the rune for a
string when we upgrade to tcell v3.
