Design: the quiet disclosure becomes a §5 component used by its four pages, and quiet-details leaves §5d #3925

For: the design audit (#2678). DESIGN.md §5d says a page-local class that turns out to be a component moves into §5's table. .quiet-details (a <details> with a quiet chevron summary) is used by src/web/pages/looks.ts, src/web/pages/pull-spec.ts, src/web/studio/feed.ts and src/web/studio/tell.ts, with rules in src/web/style/content.ts, and is restyled in src/web/studio/feed_style.ts.

Done:

• [ ] src/web/ui.ts gains one helper, disclosure(summary, body, o?), that draws the <details>. The four call sites use it, and the HTML they produce keeps the same summary text and body.
• [ ] The rules move from style/content.ts to style/components.ts under one §5 class name. The name leaves the style/content.ts bullet of §5d and gains a row in §5's table. feed_style.ts keeps its 44 px touch target, against the new name.
• [ ] bun scripts/design-lint.ts passes, and --update gives a lower or equal baseline.
• [ ] A test calls disclosure and checks its markup, and asserts quiet-details appears nowhere under src/web. The existing tests of the four pages pass. Run bun x tsc --noEmit before the push.

Files: src/web/ui.ts, src/web/style/content.ts, src/web/style/components.ts, src/web/studio/feed_style.ts, the four pages, docs/DESIGN.md, the test. Risk: escaping. disclosure takes Html or plain strings, and escapes strings like every other ui.ts helper. Screenshots are not required.

Parked by the crew: the check failed in the place it ran, not in the change, and failed the same way when it was run again (pull #3933 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Steward (trevato): pull #3933 was parked by an infrastructure fault, not this work - the egress cap from #3719 stopped every check's package install (02:20-03:12Z). The forge is rolled back and the cap is fixed (c7ea1935). Reopened and re-checked; this strike does not count.