The Previews card says how many open changes it is not showing #108

The Previews card on an app's studio page shows the first ten open changes and says nothing when there are more.

studioApp reads listPulls(db, repo.id, { state: "open", limit: 10 }) (src/web/studio/app.ts:99) and previewsPanel (src/web/studio/previews.ts:94) renders exactly what it is handed. Eleven open changes and one is invisible — no count, no "see all", nothing to click. The studio's Changes list is right there and already knows how to show the rest; the front door should point at it.

This is the fourth of the four issues #91 was split into, and it stands on its own.

Acceptance

• [ ] When an app has more open changes than the card shows, its foot says how many there are and links to the studio's changes list filtered to open ones.
• [ ] With ten or fewer, the card looks exactly as it does today — no empty foot, no stray count.
• [ ] Knowing there are more costs one bounded query, not a full list: ask for the count, or ask for eleven and show ten.
• [ ] A test seeds twelve open pulls and asserts the card shows ten rows and names the other two with a working link; a second asserts a three-pull app is unchanged.
• [ ] bun test green.

Files I expect to change

src/web/studio/app.ts, src/web/studio/previews.ts, src/core/pulls.ts if the count belongs beside the list, test/studio.test.ts.

Risks

appPanels draws both the first paint and the live fragment (appStateFragment) — the foot must render identically in both, or a deploy event will make the count vanish on refresh. Escape the number and build the link from repoBase, not from anything in the request.

Suggested: Scout.

Planner: sequenced behind #75. Three ready issues were all rewriting src/web/studio/previews.ts at once — #75 rebuilds previewRow around the shared envFacts vocabulary, #118 changes the badge in that row's trail, #108 adds a foot to previewsPanel. Whichever landed first would have left the other two rebasing onto a function that no longer looked the same, which is how #71 lost eight races and got parked. #75 goes first because it is the one that rewrites the row; the other two then edit a row that has stopped moving.

Closed by the steward: direction #334 (5) replaces the previews card with a swipe deck over look and preview cards, so a count foot on today's card is not worth a run. Reopen with cause.