The page plays a camera's H.264 through video-pane.js when it offers it and WebCodecs exists, and falls back to the frame feed when no picture comes within 3 s #383

From #260, piece 2 of 2 (#70 real video).

Done:

• [ ] Software/so101/src/viewer.html imports src/ui/video-pane.js (dynamic import, only for a camera whose /cameras entry has h264: true in a browser where canDecode() is true) and plays /camera/<id>/video through VideoPlayer. When the player reports no support or no picture within 3 s, the camera falls back to the existing /camera/<id>/ws frame feed (src/ui/video.js) without changing the camera box's size.
• [ ] The quality select appears only while H.264 plays.
• [ ] A test (pure helper or served-page assertion like the existing ones) covers the fallback choice and that a camera with h264: false never loads video-pane.js.
• [ ] The first-visit gzip budget test passes without shortening existing comments. bun --cwd Software/so101 test passes.