Ctrl-C interrupts agent instead of clearing prompt edit box

Description

Ctrl-C now interrupts the running agent instead of clearing the prompt edit box. This is a regression from previous behavior where Ctrl-C would clear what you were typing in the input field.

Expected behavior

When the prompt edit box has focus and contains text, Ctrl-C should clear the text in the edit box (standard terminal line-editing behavior).

Actual behavior

Ctrl-C sends an interrupt to the running agent, causing [Request interrupted by user] even when the user just wants to clear their typed input.

Severity

URGENT — This makes it very difficult to correct typos or abandon partially typed prompts without accidentally interrupting in-progress work.