fix(detail): mount the zoom viewer when opened via the fullscreen (⛶) button

[Zheaoli]

Symptom

Clicking the fullscreen (⛶) button on a photo opened a blank zoom area — "can't load zoom." Happens on every device; it is not a WebGL/GPU issue — the viewer simply was never mounted.

Root cause

The ⛶ button's onClick only set lightboxPhoto = true. It did not add the photo to the zoomed-viewer LRU, unlike the image-click path:

// image click (had the bump):
onShowLightboxChange = (value) => { setLightboxPhoto(value); if (value) bumpZoomLru(photo.id) }
// ⛶ button (missing the bump):
onClick = () => { setLightboxPhoto(true) }   // ← no bumpZoomLru

With the LRU mount-gate added earlier (keepViewerMounted={zoomLru.includes(photo.id)} → progressive-image gates the viewer on hasOpenedFullScreen && keepViewerMounted !== false), a photo opened via ⛶ was never in the LRU, so keepViewerMounted was false → false !== false → the WebGL viewer <div> never rendered → blank. The two zoom-open paths were asymmetric; the mount-gate was added without updating the ⛶ path.

Fix (both, complementary)

• A — the ⛶ button now also calls bumpZoomLru(current?.id), mirroring the image-click path. bumpZoomLru now ignores a falsy id defensively.
• B — the mount-gate also keeps the currently-open photo mounted regardless of which path opened it:
  keepViewerMounted={zoomLru.includes(photo.id) || (isCurrent && lightboxPhoto)}.
  This root-fixes the whole class (any route that sets lightboxPhoto) and does not relax the LRU's ≤3 cap — the current photo should always be mounted; the rest stay LRU-bound.

tsc + eslint clean. The viewer-lifecycle / GL-context LRU behavior is otherwise unchanged. (Verification needs a real GPU browser — the fullscreen WebGL viewer can't be exercised headless; the fix is that the viewer <div> now mounts on the ⛶ path, which is environment-independent.)

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Project	Deployment	Actions	Updated (UTC)
picimpact	Ready	Preview, Comment	Jun 11, 2026 8:44am

[Zheaoli]

Duplicate of #528 (same A+B fix), which is already Review-approved. Closing in favor of #528.