Add generated syntax themes from the system accent color

[culpen90]

Description

Adds an opt-in theme mode that derives editor syntax colors from the macOS system accent color.

• Supports complementary, monochromatic, analogous, triadic, and tetradic color harmonies.
• Refreshes generated palettes when the system accent or appearance changes.
• Preserves the selected base theme, syntax styling, and terminal colors.
• Enforces readable syntax and insertion-point contrast against the editor background.
• Adds a native Settings control, strategy picker, generated palette preview, and regression coverage.

macOS applies wallpaper-derived Desktop Tinting while rendering materials but does not expose that tint as a serializable color value. This option therefore uses NSColor.controlAccentColor and labels the source as the system accent color.

Related Issues

• Closes ✨ Automatically Generated Color Themes based on window tint color #46

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