Better handling for incorrect characters typed in Command Mode

Story:
- user is in command mode
- user attempts to type into the terminal
- probably the first character isn't a shortcut, but pretty quick they stumble into one, and a surprising shortcut action takes place
- all the destructive ones have confirm screens, so little risk of a big problem, but it's not great

Possible better answer:
- when a wrong character is typed, a modal pops up

```
That's not a shortcut!
Press [Enter] if you meant to type into the terminal in PASSTHROUGH mode
Press [Esc] to return to COMMAND mode

Recognized shortcuts are:

```

No file or test is named in the issue. Start by locating the command-mode input handling and modal components, then trace how unrecognized characters are processed. Done means an incorrect character opens the described modal, Enter switches to PASSTHROUGH mode, Esc returns to COMMAND mode, and recognized shortcuts are listed.

Written by the indexing model from the issue text.