`learn keys` dialog has rough edges

[ossi]

i managed to map enter to '/', with the expected consequences for usability.

this obviously shouldn't be even possible to start with.

but that experience shows another thing: the ui offers no (obvious) way to unmap keys.

it's also woefully incomplete, with no way to map the various modified keys.

so i wonder whether the dialog as it currently exists even makes sense. maybe it would be better to replace it with a text editor for the config file's mapping section for the given terminal, or even just a hint what to do.

the alternative would be beefing it up significantly, using a hierarchy or a scrollable view to have enough space for everything.