Fix terminal Control input on non-Latin keyboard layouts

[ERuban]

Closes #612

Summary

Fix layout-dependent terminal Control-key input in Supacode tabs.

When a non-Latin macOS input source is active, interactive terminal programs such as Claude or Codex may not receive plain terminal Control chords consistently. For example, pressing the physical ⌃C keys with a Russian layout selected may not cancel/exit the program, while the same physical shortcut works after switching back to an English layout.

This change resolves plain terminal Control chords from the physical keyCode using the US-QWERTY key position before passing input to Ghostty. Regular text input remains layout-aware, and app/menu shortcuts are not affected.

Type of change

• Bug fix (the linked issue is a bug report)
• Feature (the linked issue is a feature request marked ready)
• Documentation
• Other (please describe)

How was this tested?

• make check passes (format + lint)
• make test passes
• I built and ran the app to confirm the change works

make test and make build-app could not run locally because my machine has Xcode 27, and the project preflight requires a Zig-linkable Xcode/macOS SDK combination.
I'd appreciate it if someone could test it.

AI tool disclosure (optional)

• Model(s): GPT-5
• Harness / tools: Codex

Checklist

• This pull request is linked to an issue with Closes # above.
• For a feature, the linked issue is labeled ready.
• I am the author of this work and accountable for it; no commit is authored or co-authored by an AI agent.
• I have read the Contributing guide and the Code of Conduct.

[sbertix]

Adding it here too since it went unnoticed in the issue.

Is this reproducible in Ghostty, by any chance? @ERuban
Because, if so, this should possibly be deferred to the Ghostty lib itself.