Credibility pass: the seams get sanded

Scoped to everything since the last pass (3308850). Three blind
reviews, every finding verified before touching anything.

Confirmed and fixed: two identical comment-splitting insertions left
doc comments orphaned from their fields (net and local alike); a
51-line CSS fossil of the pre-extraction inline effects survived in
Board.svelte; the rev-13 miss-roll test asserted tautologies while
its comment claimed a check the code never made — it now proves the
die was consumed, and the skeleton is no longer returned as trollId;
the sprite registry's `as never` silently disabled the completeness
its annotation advertised (now a mapped type, one cast at the
dispatch seam); a dead ternary guarded a union that doesn't exist;
Bolt carried a duplicate .fork rule from a color iteration; fxTtl
contradicted three sprites' real animation lengths; the permanence
sentinel was reinvented as a magic 9000 (the engine now exports
isPermanentDuration); CELL was declared thrice (fx.ts now imports
it); App and Replay ran two divergent fx schedulers (one scheduleFx
now, cancellable — stale flourishes can no longer fire after leaving
a game); TokenArt retried missing files forever; the anti-anti
escape guards merge with the gate asymmetry explained; wall-of-fire's
rev-12 carve-out is marked; overLimit ignored a displayed BRAINSTONE
(bots over-discarded by two); botRemark's header mis-stated its own
branches; deliverGold fired on any drop, not a home-base delivery;
escape and win banter never fired from the steps that carry them.

Rejected: "as a human would" (house voice); FxGallery's dev-harness
framing (trimmed one plea, kept the facts).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packages/web/src/TokenArt.svelte

@@ -7,7 +7,7 @@
   // are cached per URL, with their ids namespaced so 45 tokens' worth of
   // filter/pattern defs cannot collide in one document.
   type Entry = { vb: string; inner: string };
-  const cache = new SvelteMap<string, Entry | "pending">();
+  const cache = new SvelteMap<string, Entry | "pending" | "failed">();
 
   function load(href: string): void {
     if (cache.has(href)) return;
@@ -24,7 +24,9 @@
         const vb = m ? (/viewBox="([^"]*)"/.exec(m[1]!)?.[1] ?? "0 0 144 150") : "0 0 144 150";
         cache.set(href, { vb, inner: m?.[2] ?? "" });
       })
-      .catch(() => cache.delete(href));
+      // A failed fetch stays failed: deleting would retrigger the effect
+      // and hammer a missing file forever.
+      .catch(() => cache.set(href, "failed"));
   }
 </script>
 
@@ -49,7 +51,7 @@
 </script>
 
 {#if isSvg}
-  {#if entry && entry !== "pending"}
+  {#if entry && entry !== "pending" && entry !== "failed"}
     <svg {x} {y} {width} {height} viewBox={entry.vb}
       preserveAspectRatio="xMidYMid slice" class={cls}>
       {#if title}<title>{title}</title>{/if}