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.

docs/manual/README.md

@@ -359,6 +359,8 @@ It opens in develop all the same, on a reduced copy that is drawn from the
 full resolution wherever you zoom in, and it exports at full size. The same
 goes for a panorama Lightroom stitched and saved as a DNG.
 
+![A 22 927 × 8966 panorama of a glacier at dusk: zoomed from the whole frame into the peaks, panned along the ridge and back out, then 1:1 on the peaks with a double-click](media/giant-pano.gif)
+
 ![Twelve frames aligned, the first left out and brought back, the projections tried, and the border filled](media/panorama.gif)
 
 ![The alignment on a cylinder, each frame outlined where it landed](media/panorama-aligned.png)

docs/manual/index.html

@@ -400,6 +400,7 @@ preview and in the composite.</p>
 It opens in develop all the same, on a reduced copy that is drawn from the
 full resolution wherever you zoom in, and it exports at full size. The same
 goes for a panorama Lightroom stitched and saved as a DNG.</p>
+<figure><img loading="lazy" src="media/giant-pano.gif" alt="A 22 927 × 8966 panorama of a glacier at dusk: zoomed from the whole frame into the peaks, panned along the ridge and back out, then 1:1 on the peaks with a double-click"><figcaption>A 22 927 × 8966 panorama of a glacier at dusk: zoomed from the whole frame into the peaks, panned along the ridge and back out, then 1:1 on the peaks with a double-click</figcaption></figure>
 <figure><img loading="lazy" src="media/panorama.gif" alt="Twelve frames aligned, the first left out and brought back, the projections tried, and the border filled"><figcaption>Twelve frames aligned, the first left out and brought back, the projections tried, and the border filled</figcaption></figure>
 <figure><img loading="lazy" src="media/panorama-aligned.png" alt="The alignment on a cylinder, each frame outlined where it landed"><figcaption>The alignment on a cylinder, each frame outlined where it landed</figcaption></figure>
 <figure><img loading="lazy" src="media/panorama-filled.png" alt="The same, with the ragged border filled by the model rather than cropped away"><figcaption>The same, with the ragged border filled by the model rather than cropped away</figcaption></figure>