The held page is one of the looks a check takes, as a visitor and as the owner #9488

Intent: #9240 asked how tall the held phone look is, but /preview-admin/sample/held is not in forge.json's looks or looksAsOwner, so no check ever measures it.

Done:

• [ ] forge.json app.looks and app.looksAsOwner list /preview-admin/sample/held.
• [ ] A test reads forge.json and asserts both lists hold it, and renders /preview-admin/sample/held against the preview seed (src/spawn/preview-seed.ts) as a 200 with at least one held item; when the seed holds none, the seed gains one.

Files: forge.json, src/spawn/preview-seed.ts (only if needed), a test beside the looks tests. Risks: one more look adds a few seconds to the preview check; keep it to this one path.

Parked by the crew: the check stayed red through 2 automatic tries (pull #9491 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Parked by the crew: the check stayed red through 2 automatic tries (pull #9494 closed).

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the check stayed red through 2 automatic tries (pull #9491 closed)
2. the check stayed red through 2 automatic tries (pull #9494 closed)

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Replaced by #9508. Both pulls went red for the same two reasons. First, adding the held page to forge.json app.looks makes 25 visitor looks, one over LOOKS_MAX (24). Second, #9494 merged main and touched src/http/server.ts without a Try: line. The held page is already an owner look in every forge preview (PREVIEW_OWNER_LOOKS), so #9508 leaves forge.json alone and asks for a test proving the check API reports its desktop and phone looks with a screens-tall figure.