[codex] simplify Photos image viewer

[philipnee]

Why

The Photos app should feel like a dedicated image viewer, not another dashboard table. In relay testing, burst-loading many images dropped the tunnel and left broken thumbnail placeholders. Refresh made this worse: browsers may revalidate cached images, so even fast 304 responses can still traverse the relay and hit rate limits.

What changed

• Restyles the Photos app into a sparse masonry image viewer with the same visual language as pnee.uk/life.
• Removes dashboard chrome, sidebar, status text, captions, download controls, and the visible “show more” control.
• Keeps only breadcrumb/source navigation, clickable folders, the photo grid, and a full-screen lightbox.
• Loads only a smaller DOM batch at a time and appends additional tiles instead of re-rendering already-loaded images.
• Uses an IntersectionObserver so image network requests start only when tiles approach the viewport.
• Keeps the capped FIFO image queue and paces image starts by 250ms so cached 304 responses cannot drain the whole queue in one burst.
• Drops HEIC/HEIF from browser-previewable images for now to avoid guaranteed broken previews in Chrome.

How

Photos still uses only the shared cookie-authenticated FS API: /api/fs/sources, /api/fs/list, and /api/fs/file. It renders folder buttons separately from the masonry photo grid, observes each photo tile before assigning src, and pushes image tasks through a paced queue. Infinite scrolling appends the next batch of tiles instead of rebuilding the grid, so scrolling does not replay old cached image requests. Clicking a photo opens the same file URL in a minimal lightbox.

Out of scope: server-side thumbnails, HEIC transcoding, relay-side rate-limit splitting, /api/fs/list pagination, and a separate photo metadata API.

Changed files

• src/apps/photos/manifest.ts - replaces the dashboard-style Photos UI with the minimal masonry/lightbox viewer, viewport-driven image loading, and paced request queue.
• tests/server.test.ts - updates app-serving assertions for the simplified viewer, queue, auto-load sentinel, viewport observer, and no extra dashboard chrome.

Verification

npm test -- tests/server.test.ts

Test Files  1 passed (1)
Tests  103 passed (103)

npm run verify

Test Files  44 passed (44)
Tests  456 passed (456)
ok: test
ok: diff whitespace
ok: package dry-run
ok: runtime smoke
verify passed