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/README.md

@@ -47,6 +47,12 @@ manual does not show; it reads two files and runs in CI. `--changed`
 re-records a scene when one of its sources, or its own code, has changed
 since the commit that last touched its pictures.
 
+GIFs are made at 960 px and ten frames a second. A scene whose film does
+not compress at that size says otherwise in `GIF_SIZE`, which `record.sh`
+reads through `scenes.py gif NAME`. `giant_pano` borrows a 500 MB panorama
+from outside the library (`DR_GIANT_DNG`, by default
+`/var/tmp/dr-dng/IMG_4181-Pano.dng`) and removes it again, so it runs last.
+
 Two things the scripts know that are not obvious: a Slint `TouchArea` wants
 a held press, not xdotool's `click`; and the app is driven on Xvfb rather
 than the desktop because under XWayland at scale 2 a pointer warp lands at