Bind escape and q to exit without running anything

[Julian]

This adds a key binding for exiting the TUI via the same key bindings as closing modals.

ISTM perhaps it'd be nicer for escape to be bound to work sort of like a back button, so that if you hit it in the right pane of the TUI you "jump outward" back into the left sidebar. But that is obviously more work than just this 3 line change (and seems more subjective). I'm not sure I can commit to figuring out how to wire that in even if interested, but let me know what you folks think.

[fresh2dev]

These are my interpretation of vim-friendly hacker 🥷 keybindings:

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From the command tree:

• enter to focus the selected command.
• j to move down one command.
• k to move up one command.
• g to go to top.
• G to go to bottom.
• u to page-up.
• d to page-down.
• ? to show command help.
• / to focus search.
• q to quit without running.

From the selected command form:

• escape to focus the command-tree pane.

Globally:

• ctrl+y to copy the command text to clipboard.