A where line's dot separator draws components.ts's .sep, and .where-sep leaves the markup #4280

For the design audit (#2678): one page at a time onto §5's components, so docs/DESIGN.md §5d only shrinks. Part one of two: this part changes only the markup; the stylesheet and docs/DESIGN.md are part two.

Done:

• [ ] Every · separator that now wears .where-sep wears .sep from src/web/style/components.ts (or a ui.ts helper that draws it, if one exists; name which in the pull), still aria-hidden="true". None of .where-sep appears in any page's HTML.
• [ ] A separator inside .row-meta keeps its 3px side margin and its faint colour by eye (if .sep differs, say how in the pull, but do not add a new class).
• [ ] Do not delete the rules from src/web/style/content.ts and do not edit docs/DESIGN.md: part two does that.
• [ ] A test asserts where-sep is absent and the separated words are present on a pull page and an origins page.

Files: src/web/pages/origins.ts, src/web/pages/pull.ts, src/web/pages/site.ts, src/web/studio/change.ts, src/web/scope.ts, a test. Before pushing, run bun x tsc --noEmit, bun test test/design-lint.test.ts, bun scripts/design-lint.ts and those pages' tests. No screenshots: the sandbox has no browser.