Mobile media: full-screen tap dead while the signed URL loads

Status summary: done. Fix landed on PR #2545; the previously-failing spec passed on the PR's own Cloudflare preview run first-attempt (28.0s). Spec unchanged.

specs/mobile/media.spec.ts ("renders, searches, and views seeded media") fails deterministically on Cloudflare-preview CI at line 81 — after clicking "View full screen", getByLabel("Full screen media") never appears — while passing against local dev.

Diagnosis#

The failure screenshot + accessibility snapshot from the preview run show the media row expanded (transcript, filename, Re-analyze visible) and no viewer. MediaRow's thumbnail pressable wears accessibilityLabel="View full screen" from first render but is disabled={imageUri === null} while the signed-URL query (project.files.get(path).url()) is in flight. A tap in that window is swallowed by the disabled pressable and falls through to the outer row pressable, which expands the row instead. No spinner exists in that window, so the middlewright spinner-waiter has no loading UI to extend on ("Timeout 1ms exceeded"). Local dev resolves the URL fast enough that the click wins the race; preview deployments (real network, cold worker, KV + R2 head) lose it.

NoteThumb in notes.tsx has the identical pattern (disabled={imageUrl.data === undefined}).

Not relevant: the forged-session fixture helpers — signup succeeded in both failing runs, and mobile specs authenticate through the app's own OAuth popup, not an OS-origin cookie.

Fix#

• MediaRow (media.tsx): render the "View full screen" pressable only once imageUri exists; while the URL query is pending, show the placeholder thumb with an ActivityIndicator accessibilityLabel="Loading" — real loading UI, and the spinner-waiter cue that keeps the spec's wait budget extended until the label appears. Done in media.tsx; the label is now a promise the control works.
• NoteThumb (notes.tsx): same gating for View <filename>. Same change shape.
• Spec untouched — no timeout bumps. The spinner-waiter picks up the new spinner via its [aria-label="Loading"] selector.