Design: a run's summary line and cancel actions use §5's text and bar, and run-summary/run-actions leave §5d #3960

For: the design audit (#2678). One page part at a time onto §5's components (src/web/ui.ts helpers such as row, card, badge, btn, and §5 classes), so docs/DESIGN.md §5d only shrinks.

src/web/studio/run.ts draws <p class="run-summary" id="run-summary"> and <div class="run-actions" id="run-cancel"> (two places), styled in src/web/style/content.ts.

Done:

• [ ] The summary is a plain paragraph with base utilities (.mt and friends), and the actions use base's .bar with §5's btn. The ids run-summary and run-cancel stay: src/web/client.ts finds them by id and must keep updating them live. Every form posts the same fields.
• [ ] Those classes' rules are gone from src/web/style/content.ts, and their names leave the apps/runs/crew bullet of docs/DESIGN.md §5d. bun scripts/design-lint.ts passes, and --update gives a lower or equal baseline.
• [ ] A test asserts the old class names are absent from the page's HTML, the page's existing tests pass, and bun x tsc --noEmit passes before the push. Screenshots are not required; the sandbox has no browser.

Files: src/web/studio/run.ts, src/web/style/content.ts, docs/DESIGN.md, the test. Risk: #3873 edits the check steps and pinned failures on the same page: keep to these two classes.