feat(ui): add Cursor editor theme

[priyanshuwq]

Summary

• Added the "Cursor" theme to ghui.
• Mapped the official Anysphere Dark theme palette (Cursor's default editor theme) into ghui's terminal UI color model, capturing the distinct charcoal background and signature bright blue accents.

References

• The Cursor editor theme draws from the standard VS Code Dark+ palette but applies Anysphere's custom refinements (e.g., deep #181818 background, #228df2 accent blue).

Screenshots