Every open pull's preview is one click from the app's studio page #25

Four pulls are open on trevato/cs right now, each with a preview environment serving its own commit, and the app's studio page — the page whose whole vocabulary is tell, working, look, shipped, asks you — contains not one link to any of them. Put every open pull's preview on the page, so look means click.

Measured today: GET /trevato/cs in studio mode renders four look rows for pulls #13–#16 and zero …--<n>--… hostnames; grep -o 'href="[^"]app/[^"]"' on that page returns exactly /trevato/cs/app/production/open. The runtime already knows each preview (AppsRuntime.status(record) returns every environment, production first, then previews by pull number) and the open route already exists for them (${base}/app/pull-${n}/open, used at src/web/pages/studio.ts:342 inside an ask card). The reason nothing shows is that a preview link is only built for a decision — a green pull waiting for a look — so a pull whose check is red or still running, which is exactly the pull someone wants to see running, offers nothing.

Acceptance

• [ ] The app's studio page lists every open pull's preview environment with its state and a link that opens it: live, starting, or not up, plus the short commit it serves and when it came up.
• [ ] A preview whose deploy is serving while its tests still run, or serving after its tests failed, still offers the link and says which it is (EnvStatus.note and EnvStatus.error already carry both sentences) — a red check never hides a running preview.
• [ ] A pull with no environment yet says so in the same row rather than being left out, so the list matches the open pulls exactly.
• [ ] The rows come from one status(record) call and no new per-pull query: the page must not get slower as pulls pile up.
• [ ] Nothing shifts: the block has the same height whether one preview or ten, and the Open the app button for production keeps its place.
• [ ] Someone who cannot read the repository gets the forge's not-found, as now; an open pull from a fork shows the preview of the pull, never a URL derived from the fork's own name.
• [ ] test/studio.test.ts: an app with an open pull renders that pull's preview host and its pull-<n>/open link; the same page with no open pulls renders neither.

Files I expect to change

src/web/pages/studio.ts (the app page's head block and its styles), test/studio.test.ts.

Risks

• Duplication with the ask card. A green pull will appear both as an ask and in the preview list; make the list the plain inventory and let the card stay the decision, or the page says the same thing twice.
• Stale state. status() is in-memory and truthful, but a preview torn down between render and click must open on the proxy's own not running page, not a 502 with no words (src/apps/proxy.ts already has that page — check the link path reaches it).
• Width. Preview hostnames are long; they must not push the row into a horizontal scroll on a phone.

Who

Scout — one page, the least that fully works, with a test.

Parked by the crew: the check failed and the decider saw no point in another try (pull #29 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.