A repository's Settings › Prompts speaks the home page's language #9825

/:owner/:name/settings/prompts is the last steering settings page still built of boxed cards. It should read like the home page and the settings pages already converted (#9809 Labels, #9796 Trusted): one heading, the prompt sources as a plain list, the add form on the page.

Done looks like:

• [x] src/web/pages/prompts.ts renders the page without card( or card-body: one <h1>, the list of sources (each with its run and delete actions, or the empty sentence) and the add form as plain sections.
• [ ] A new test/prompts-language.test.ts fetches the page as an admin of a seeded repository, once with no source and once with one, and asserts inside <main> one <h1>, no class="card and no card-body, the add form posting to /:owner/:name/settings/prompts, and the run and delete forms for the seeded source. It fails on main today.
• [x] test/prompts.test.ts and test/prompts-etag.test.ts still pass; bun scripts/design-lint.ts passes. Any new class goes in docs/design/areas/settings.md, not docs/DESIGN.md.

Files: src/web/pages/prompts.ts, test/prompts-language.test.ts, maybe docs/design/areas/settings.md. Risks: the ETag test pins the response for an unchanged list; keep every form's same-origin POST and its action path unchanged.

Reviewed pull #9839 at its head: ticked src/web/pages/prompts.ts renders the page without card( or card-body: one <h1>, the list of sources (each with its run and delete actions, or the empty sentence) and the add form as plain sections.; test/prompts.test.ts and test/prompts-etag.test.ts still pass; bun scripts/design-lint.ts passes. Any new class goes in docs/design/areas/settings.md, not docs/DESIGN.md..

Left open after pull #9839 landed: 1 unticked item remains (A new test/prompts-language.test.ts fetches the page as an admin of a seeded repository, once with no source and once with one, and asserts inside <main> one <h1>, no class="card and no card-body, the add form posting to /:owner/:name/settings/prompts, and the run and delete forms for the seeded source. It fails on main today.). The planner files each as its own issue and closes this one; a person may close it, tick what is done, or say what is left. Until then the crew does not pick it again.

Already done on main in 65160ec88: test/prompts-language.test.ts asserts one <h1>, no class="card/card-body, the add form with no source, and run/delete forms for a seeded source. The open box is met; closing as done.