Release CSS Loader for Millennium 1.0.0 - #4

Summary

• promote CSS Loader for Millennium from preview to the stable 1.0.0 release
• replace generated-theme translation with direct resolved-CSS publication and companion injection
• preserve CSS Loader themes, configurations, dependencies, patches, variables, assets, inline SVG/data URLs, and animations
• synchronize styles across Steam windows with atomic runtime state and content hashing
• pin CSS Loader Companion for Millennium v1.0.0
• add complete 1.0 highlights, feature coverage, advantages, and installation documentation

Validation

• npm run verify
• 11 backend regression tests
• companion production build
• desktop TypeScript and Next.js production build
• Tauri release build
• Windows x64 MSI produced successfully
• newly built backend restarted and running from the release output