Fix keybind capture

[Razr7315]

The keybind field was clearing its value as soon as it was focused, so it saved nil when the click didn’t register as a valid key input. It now keeps the previous bind unless a valid key is selected, and mouse clicks no longer trigger bound actions.

[maxtcodes]

I found one issue that should be fixed before merging.

The new keybind capture flow retains the old bind when focus is lost, but it also removes the only way to clear an assigned keybind and return it to "No Keybind."

The rest of the keybind changes look consistent, and CI is passing. Once users can clear an assigned bind without reintroducing the accidental clear bug, I think this will be ready for Jenson to review and merge.

Requesting changes for the inline issue above.

[Razr7315]

Fixed. Losing focus now cancels key capture and restores the previous bind, while pressing Backspace or Delete sets it to “No Keybind.”