[Juliusolsson05]

Summary

• replace hashed worktree badge colors with a centralized badge color utility
• reserve fixed colors for main and master branches
• assign non-main worktree colors from a curated 30-color palette in first-seen order
• add work-context tests for fixed branch colors and chronological palette assignment

Verification

• npm run test:work-context
• npm run build
• git diff --check