Wrap seventeen moons and dwarf planets in the missions' own maps, grey where no probe looked

Audit #40. Io, Titan and Pluto had square disc photographs (40.5, 42.6 and
42.9% black sky) that PR #33 unlisted, and every other moon or dwarf planet
fell through to the derived surface. Seventeen of them are now wrapped in
public-domain global mosaics from USGS Astrogeology and the NASA PDS: Phobos
(Viking), Io, Europa, Ganymede, Callisto (Galileo and Voyager), Mimas,
Enceladus, Tethys, Dione, Rhea, Titan, Iapetus, Phoebe (Cassini), Triton
(Voyager 2), Ceres (Dawn), Pluto and Charon (New Horizons). io.jpg, titan.jpg
and pluto.jpg are replaced by maps under the same names.

Every file is simple cylindrical over 360 by 180 degrees, with longitude 0 in
the middle and east to the right, the frame MAP_TO_BODY puts on the IAU body
frame. Processing: the source's no-data pixels (0 in every band) become one
flat grey, the mean of the mapped surface, never invented terrain; area
downsampling to 2048x1024 for bodies over 1 000 km in radius and 1024x512
for the rest; half a turn where the source is centred on 180; JPEG q85
(Europa q82). Largest file 386 KB (Europa); 3.5 MB for all seventeen.

The centre was read from each GeoTIFF's central meridian and left-edge tie
point, not from its label: Rhea's and Enceladus's labels say CENTER_LONGITUDE
= 180 over images centred on 0. Taken from the label, Rhea came out half a
turn round, which the seam it left down the middle of the map gave away.
Each map was then checked by eye against the IAU Gazetteer: Pele and Loki on
Io, Pwyll on Europa, Osiris and Tros on Ganymede, Valhalla and Asgard on
Callisto, Herschel on Mimas, Ali Baba and Aladdin on Enceladus, Odysseus on
Tethys, Creusa on Dione, Inktomi on Rhea, Xanadu, Shangri-La and Belet on
Titan, Cassini Regio on Iapetus, Jason on Phoebe, Occator and Haulani on
Ceres, Stickney on Phobos, Sputnik Planitia and Cthulhu on Pluto, Mordor
Macula on Charon, Leviathan Patera on Triton.

Unmapped share, now grey: Triton 38.6%, Charon 34.0%, Pluto 31.9%, Phoebe
20.4%, the Galilean polar gaps 3.6-4.3%, Ceres's south pole 3.6%, the rest
under 0.2%. Pixels darker than 8 of 255: at most 0.55% (Charon's Mordor
Macula, Pluto's Cthulhu), against the 20-43% black sky of the photographs
PR #33 dropped.

Left out, and said so in src/assets/textures/README.md: Deimos, whose only
cylindrical map (Stooke, Viking) has no label for its longitude direction and
on which neither Voltaire nor Swift could be found to settle it; the five
Uranian moons, whose only maps (Schenk 2020, USRA) carry no licence; Hyperion,
Nereid, Proteus, Eris, Haumea and Makemake, which have no photographic
simple-cylindrical map.

Source URLs, credits, licences, processing and each measurement are in the new
src/assets/textures/README.md; the root README now points there and counts
twenty-seven bodies in real photography. texture-catalog.spec.ts checks that
the seventeen are registered and that Deimos, the Uranian moons, Hyperion and
Eris are not. Unit suite 790 -> 792 tests.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

README.md

@@ -134,9 +134,11 @@ its own readout, so a stale image is visible as one.
 
 ### On surfaces that were never photographed
 
-Fifteen bodies here have a real photograph. Everything else does not, and never will on current
-instruments: no exoplanet's surface has ever been imaged, and a few of the solar system's own
-moons have no usable map in this asset set either.
+Twenty-seven bodies here are wrapped in real photography: the Sun, the eight planets and the Moon,
+and seventeen moons and dwarf planets in mission mosaics, grey where no probe has seen them
+(`src/assets/textures/README.md`). Everything else is not, and no exoplanet ever will be on
+current instruments: none has had its surface imaged. Deimos, the five large moons of Uranus and
+a few small bodies have no map in this asset set either.
 
 Those bodies get a surface reasoned from what *has* been measured, in a chain that is worth
 following because every link is standard:
@@ -327,4 +329,4 @@ Star catalogue: [HYG database](https://github.com/astronexus/HYG-Database) (Hipp
 Bright Star, Gliese) — 68 388 stars within 250 pc. Solar-system ephemerides: NASA/JPL Horizons. Exoplanets: NASA Exoplanet
 Archive. Deep-sky objects: [OpenNGC](https://github.com/mattiaverga/OpenNGC). Body and skybox
 imagery: NASA/JPL/USGS public domain and Solar System Scope (CC BY 4.0) — per-file provenance
-is recorded in `src/app/shared/rendering/texture-catalog.ts`.
+is recorded in `src/assets/textures/README.md`.