feat(gui): add terminal context menu

[elonnzhang]

Summary

Add a native macOS context menu to terminal panes so common actions are accessible with a right-click.

The menu includes:

• Paste
• Search
• AI Chat
• Command Palette
• Split pane in four directions
• Close Pane

The context menu appears when the terminal application has not captured the right-click event. Holding Shift also allows it to be opened when mouse reporting is active.

Implementation

• Route native context-menu display through WindowOps.
• Convert Kaku screen coordinates to macOS global screen coordinates.
• Attach existing KeyAssignment actions to native menu items.
• Preserve the existing terminal mouse handling behavior when the menu is not shown.

Verification

• make fmt-check
• make check
• make test
  • 1484 workspace tests passed
  • 15 escape parser tests passed
• make app

Related #77

[vercel]

@elonnzhang is attempting to deploy a commit to the Faberon Team on Vercel.

A member of the Team first needs to authorize it.

[youxi798]

@elonnzhang Thanks for restoring the native terminal context menu. I finished the safety edges around stable pane targeting, close confirmation, configured mouse-reporting bypass, and custom bindings.

This is merged and available in the latest Nightly: https://github.com/tw93/Kaku/releases/tag/nightly