Picture a panorama too large for one texture being navigated

A 22 927 × 8966 Lightroom panorama of a glacier, opened in develop:
the wheel in from fit to the peaks, a slow pan along the ridge at that
zoom, back out, then 1:1 with a double-click and fit with another. The
scene borrows the file from outside the demo library, copies it into a
panorama folder, restarts so the scan finds it, and deletes it and the
sidecar the app writes beside it before restarting again; it is
registered last so no other scene sees it.

The film is fine ice and rock in every frame and was 22 MB at the
usual 960 px and ten frames a second, so a scene can now name its own
GIF size (GIF_SIZE, read by record.sh through `scenes.py gif`); this
one is 640 px at eight, 8.7 MB.

tools/manual/record.sh

@@ -150,7 +150,8 @@ python3 "$scenes" record "$media" "${@:-all}"
 # GIFs for the page; the MP4s are working files and are not kept.
 for mp4 in "$media"/*.mp4; do
     [ -e "$mp4" ] || continue
-    "$here/gif.sh" "$mp4" "${mp4%.mp4}.gif" 960 10
+    read -r width fps < <(python3 "$scenes" gif "$(basename "${mp4%.mp4}")")
+    "$here/gif.sh" "$mp4" "${mp4%.mp4}.gif" "$width" "$fps"
     rm "$mp4"
 done
 find "$media" -name '*.png' -newer "$stamp" -exec optipng -quiet -o2 {} + || true