Summary

• Remove Git diff/status derived background, hover, and border fields from GitColors, theme presets, ThemeService, and static root token exports.
• Derive Git diff/status backgrounds locally with color-mix() from canonical Git semantic text colors, keeping added, deleted, changes, and intentionally distinct staged text roles.
• Prune non-contract colors.git custom-theme keys during normalization, migrate legacy persisted custom themes on load, and keep exported themes aligned with the current Git color contract.
• Lower the theme governance baseline and update docs/architecture/theme-token-optimization.md so this contraction is captured as a durable contract rule.

Metrics

Risk Review

• Kept staged as a separate Git text role because Tokyo Night intentionally differentiates staged and added states; inline added diff lines now read --git-color-added, so they are not visually mislabeled as staged.
• Existing custom themes that still contain old Git derived fields such as changesBg, addedBg, deletedBg, stagedBg, addedBgHover, stagedBorder, or pull continue to load, but colors.git is normalized to the closed Git contract before persistence/export.
• Git diff/status backgrounds now derive at consumption sites from the active theme's canonical Git colors, avoiding duplicated TS/Sass/runtime definitions while preserving visible status semantics.
• Independent subagent review was run from both architecture and product-design perspectives; the identified custom-theme persistence/export gap was fixed and re-reviewed with no remaining blockers.

Related: #1197

Verification

• pnpm run theme:color-audit:all
• pnpm run theme:visual-contract
• pnpm --dir src/web-ui run test:run
• pnpm --dir src/web-ui run test:run src/infrastructure/theme/core/ThemeService.test.ts
• pnpm run theme:color-audit:test
• pnpm run type-check:web
• pnpm run lint:web (passes with existing bitfun-canvas warnings only)
• pnpm run build:web (passes with existing Vite chunk/dynamic-import warnings only)
• git diff --check