A repository's description wears §5's muted small text, and `.repo-desc` leaves the stylesheet #6747

src/web/chrome.ts (around line 404) draws <p class="repo-desc">; src/web/style/content.ts styles it (lines 22 and 25) the same as the .repo-head p.muted.small rule beside it, and §5d still lists it.

Done when:

• [ ] The description is <p class="muted small"> under the repo head; the narrow-screen rule that gives its link a 44px target moves to .repo-head p.muted.small a.
• [ ] .repo-desc leaves src/web/style/content.ts and its line leaves docs/design/sections/5d-page-local-classes.md; bun scripts/design-lint.ts passes.
• [ ] A test renders a repository page with a description and finds it in p.muted.small and no repo-desc.
• [ ] Before/after screenshot of a repository head in light and dark in the pull.

Only this class; .repo-actions is #6503's.