Add ⌘K Clear to Start for the integrated terminal

[Borisserz]

Description

Adds the standard macOS terminal shortcut ⌘K to CodeEdit’s integrated terminal.

When the terminal view is focused and the setting is enabled (default), ⌘K clears both the visible buffer and the scrollback. Nothing is sent to the shell — only the emulator buffer is cleared, same idea as Terminal.app and VS Code.

Also adds a Clear to Start with ⌘K toggle under Terminal Settings so it can be turned off if needed.

Related Issues

• closes ✨ Add "Clear To Start" (⌘K) shortcut to integrated terminal #891

Checklist

• I read and understood the contributing guide as well as the code of conduct
• The issues this PR addresses are related to each other
• My changes generate no new warnings
• My code builds and runs on my machine
• My changes are all related to the related issue above
• I documented my code

Screenshots

N/A — no UI layout changes beyond a new Terminal Settings toggle. Behavior is keyboard-only in the terminal.

Test plan

• Unit tests for setting defaults / decode and clearToStart() clearing viewport + scrollback
• Manual: focus terminal → produce output → ⌘K → screen and scrollback cleared
• Manual: disable Clear to Start with ⌘K in settings → ⌘K does not clear
• Manual: ⌘K only while terminal is focused (does not affect editor)

Made with Cursor

[Borisserz]

Closing to resubmit with a cleaned-up commit (author attribution).