fix(editor): improve selection contrast on active lines

[bajrangCoder]

No description provided.

[greptile-apps]

Greptile Summary

This PR makes active-line backgrounds translucent in five dark editor-theme implementations so selections remain visible on the active line.

• Updates all four Catppuccin variants through their shared configuration.
• Adjusts Tokyo Night, Tomorrow Night, Tomorrow Night Bright, and VS Code Dark active-line colors.
• Adds a unit test requiring configured active-line backgrounds to use translucent eight-digit hexadecimal colors.

Confidence Score: 5/5

The PR appears safe to merge, with no concrete functional, security, or build failures identified.

The changed colors are valid CSS values, every currently registered theme satisfies the new translucency assertion, and the updated configurations preserve existing theme construction and rendering bindings.

Important Files Changed

Filename	Overview
src/cm/themes/catppuccin.js	Makes the shared active-line color translucent across all four Catppuccin variants; no actionable defect was identified.
src/cm/themes/tokyoNight.js	Replaces the opaque active-line color with a valid translucent color while preserving the theme structure.
src/cm/themes/tomorrowNight.js	Changes the active-line background to a translucent theme-compatible value.
src/cm/themes/tomorrowNightBright.js	Changes the active-line background to a translucent value suitable for its black base.
src/cm/themes/vscodeDark.js	Makes the active-line background translucent without changing selection or syntax colors.
tests/unit/editorThemes.test.js	Adds a registry-wide assertion that every configured active-line background is an eight-digit hex color with nonopaque alpha.

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