No support for unix-line-discard shortcut (ctrl + u) #481

unix-line-discard (ctrl + u, on macOS) erases everything from the cursor back to the beginning of the line — one of the most common bash/zsh line-editing shortcuts. It works in iTerm, Ghostty, Terminal.app, etc.

In Orca's terminal (v1.1.13), the keypress is intercepted/dropped and readline never sees it, so there's no way to clear a half-typed line short of holding backspace.

Same root cause as #443 / #453 (ctrl + r). Would love a systematic audit of the key-event filter rather than whitelist-patching one shortcut at a time — ctrl + e is broken too, and there are likely more (alt + b/f/d, ctrl + w/k, etc.).