feat(assets): creature artwork from the shard's own client (Phase 3)

Until now the only way a creature got a picture on this site was for an
operator to open UOFiddler on a desktop, export sprites by hand, copy them to
the web host and write a spawnAtlas.art.json naming each one. Almost nobody
did, so shard_spawn_creatures.art was NULL on every install.

The shard has had those files the whole time. Admin -> Shard -> Import now
walks its asset manifest, fetches only the sprites whose hash changed, writes
them under uploads/atlas/, asks the shard for a body id per atlas creature
(§8: it CONSTRUCTS the creature and reads Body.BodyID, which is the only thing
that is right for a shard's own custom creatures) and points each creature at
its picture. On a stock client that is 787 portraits, about a megabyte.

**The one thing v8.md §12 got wrong, and it is not cosmetic.** It says
`shard_spawn_creatures.art` "starts being filled by the import". That table is
emptied and refilled by replaceAtlas on EVERY atlas refresh, and a refresh runs
on every boot -- so a filename stored there would be destroyed by an ordinary
re-parse of the ServUO tree, with the next Update finding the client files
unchanged, reporting "nothing to do", and never restoring it. Nothing would
report a fault; the pictures would just be gone.

So the assets and the body map live in their own tables outside that blast
radius, and applyAtlas re-derives `art` on the way past as
`{ ...derived, ...operatorMap }` -- which is also the one place "the operator's
own artwork wins" is enforced, on every rebuild rather than only at import.

Smaller decisions worth not rediscovering:

- The derivation joins on the catalogue KEY, not on the body id. The simpler
  join is correct today and stops being correct the moment phase 6 adds
  body/400/a2/f0, at which point one slug matches dozens of rows.
- Filenames are content-addressed. A stable name overwritten in place leaves
  every browser and CDN serving the previous client's sprite, with the database
  row perfectly correct.
- An unchanged key whose FILE is missing is fetched again. The row and the disk
  can disagree (a wiped uploads volume, a restore from a dump), and a broken
  image on a creature page is worse than one re-fetched sprite.
- A key the shard cannot render is not a failure. Two thirds of the playable
  ghost and gargoyle bodies have no art on a stock client, and an import that
  reported eight failures every time would teach an operator to ignore the panel.
- A key that VANISHED from the manifest needs review before anything changes:
  an unmounted client volume and a deliberate downgrade look identical here.

23 new tests; 674 server and 42 client tests pass. The SQL was also run against
a real MariaDB, which is what proved the CONCAT join and the singleton CHECK.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016wDDVXWMDz82WqE1i969r4

client/src/routes/public/Atlas.jsx

@@ -45,6 +45,46 @@ function Chip({ active, onClick, children }) {
   )
 }
 
+// One creature's portrait, when there is one.
+//
+// `art` is a FILENAME under uploads/atlas/, never a path or a URL: it is either a
+// sprite the shard extracted from the operator's own UO client (docs/link/v8.md
+// §12) or a picture the operator drew and named in `spawnAtlas.art.json`, and the
+// two are indistinguishable here on purpose.
+//
+// **NULL is the ordinary case and always will be.** An install with no shard link
+// has never imported one; a shard whose host cannot render images has none; and
+// even on a complete import, two thirds of the playable ghost and gargoyle bodies
+// have no art in the client at all (§5.2). So this renders nothing rather than a
+// placeholder, and every layout around it is written to sit correctly with the
+// picture absent — which is the state the whole atlas was designed in.
+//
+// Sprites are small (a couple of dozen pixels square) and UO's art is pixel art,
+// so `imageRendering: 'pixelated'` matters: a browser's default smoothing turns a
+// 24×63 wolf into a smear at any size above its own.
+export function CreaturePortrait({ art, name, size = 40 }) {
+  if (!art) return null
+
+  return (
+    <img
+      src={`/uploads/atlas/${encodeURIComponent(art)}`}
+      alt=""
+      // Decorative: the creature's name is already beside it as text, so an alt
+      // repeating it would make a screen reader say it twice.
+      aria-hidden="true"
+      loading="lazy"
+      style={{
+        width: size,
+        height: size,
+        flex: 'none',
+        objectFit: 'contain',
+        imageRendering: 'pixelated',
+      }}
+      title={name}
+    />
+  )
+}
+
 function CreatureCard({ creature }) {
   const facets = Object.entries(creature.facets || {}).sort((a, b) => b[1] - a[1])
   return (
@@ -60,6 +100,7 @@ function CreatureCard({ creature }) {
         color: 'inherit',
       }}
     >
+      <CreaturePortrait art={creature.art} name={creature.name} />
       <div style={{ minWidth: 0, flex: 1 }}>
         <div
           className="display"