Correct four claims in the README against the tree

Eighteen declared operations, not fifteen; JPEG XL is an export format;
the grid does not filter by keyword, only the catalog's query can; and a
panorama's provenance is a sidecar beside the composite, not a history
step in it.

README.md

@@ -16,12 +16,12 @@ is still missing.
 or one a Nextcloud client keeps in virtual-files mode, where a placeholder
 is treated as the photograph rather than as a one-byte file — or at a
 Nextcloud account directly. The grid is virtualised, ordered by capture
-time with a timeline beside it, and filtered by rating, flag, keyword,
-person and whether the file is here. Ratings, keywords, collections and a
+time with a timeline beside it, and filtered by rating, flag, person and
+whether the file is here. Ratings, keywords, collections and a
 trash that survives a crash mid-operation. Card ingest. Bursts fold. Face
 detection and identity, with the index syncing between devices.
 
-**Developing.** Fifteen declared operations fused into one compute
+**Developing.** Eighteen declared operations fused into one compute
 dispatch, plus the neighbourhood work that cannot be: clarity, texture,
 capture sharpening, noise reduction, lens correction, spectral film
 simulation. Crop and straighten, spot repair, and local adjustments over
@@ -33,11 +33,11 @@ judging what is recoverable. Named presets; XMP sidecars other editors read.
 
 **Panoramas.** Select the frames, align, choose a projection, fill the
 ragged border rather than crop it, and the composite lands beside its
-sources as a DNG with the merge as the first step in its history.
+sources as a DNG, with a sidecar recording what it was merged from.
 
 [![Twelve hand-held frames aligned on a cylinder](docs/manual/media/panorama-aligned.png)](docs/manual/README.md#merging-a-panorama)
 
-**Export.** JPEG, PNG, AVIF, 8- and 16-bit TIFF, with resize, output
+**Export.** JPEG, PNG, AVIF, JPEG XL, 8- and 16-bit TIFF, with resize, output
 sharpening, a naming template and a colour space — to a folder here or back
 into the library.