Reduce main bundle size by ~44% gzipped (732 KB → 412 KB) (#4229)

## Summary

Cuts the main JS chunk from **2,891 KB (732 KB gzip)** to **1,679 KB
(412 KB gzip)** by fixing two bundling issues and removing/replacing
heavy dependencies. Measured with a per-module `renderedLength` analysis
of the rolldown output (its prod sourcemaps are malformed, so
sourcemap-based tools misattribute sizes).

| Chunk | Before | After |
|---|---|---|
| `index-*.js` (min) | 2,891 KB | 1,679 KB |
| `index-*.js` (gzip) | 732 KB | **412 KB** |

## Changes

- **Sim worker moved out of the main bundle (~512 KB).** The
`?worker&inline` payload is now reached through a dynamic `import()`, so
it lands in its own lazy chunk fetched when a game starts. The worker
itself still uses Vite's inline Blob mechanism (with its `data:` URL
fallback) — runtime instantiation is byte-for-byte unchanged.
- **Replaced `lit-markdown` with `marked` + the already-bundled
DOMPurify (~380 KB).** lit-markdown transitively pulled sanitize-html,
htmlparser2, postcss, and two copies of entities into the client just to
render news markdown. New `src/client/Markdown.ts` matches its
image-stripping default.
- **Dropped `colorjs.io` (~114 KB).** It was only used for ΔE2000
distance in `ColorAllocator`; colord's lab plugin (already imported
there) provides the same CIEDE2000 via `.delta()`. Only relative
magnitudes are compared, so allocation behavior is unchanged.
- **`msdf-atlas.json` (~319 KB) fetched at runtime** like the atlas PNG,
preloaded in parallel with worker init in `ClientGameRunner` so
game-load latency is unaffected.
- **Tailwind CSS no longer shipped twice (~158 KB).** `o-modal` imported
`styles.css?inline`, duplicating the emitted stylesheet as a JS string.
It now adopts a constructed stylesheet built from the document's own CSS
(HTTP-cache hit in prod, `<style>` tags + HMR re-sync in dev) via
`SharedStyles.ts`.
- **Debug GUI lazy-loaded.** lil-gui + `gl/debug/*` now load on first
toggle (46 KB lazy chunk) instead of shipping in the main bundle.

Also looked at the `import * as d3` in RadialMenu (~84 KB) but left it:
rolldown tree-shakes the metapackage well and all but ~2 KB is the
genuine dependency closure of the selection/transition/shape/color APIs
in use.

## Test plan

- [x] `tsc --noEmit` clean
- [x] ESLint clean
- [x] Full test suite passes (1,374 + 65 tests)
- [x] `npm run build-prod` succeeds; worker/debug chunks present in
`asset-manifest.json` for the R2 upload
- [ ] Manual smoke test in dev: start a game (worker dev path), open a
modal (shared stylesheet), open news modal (markdown rendering)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

src/client/render/gl/index.ts

@@ -1,5 +1,6 @@
 export type { AttackRingInput } from "../types";
-export { createDebugGui } from "./debug/index";
+// createDebugGui is intentionally not re-exported here — it pulls lil-gui and
+// the debug GUI into the main bundle; dynamically import "./debug/index".
 export type {
   GameViewEventMap,
   GameViewEventType,
@@ -11,6 +12,7 @@ export type {
 export { GameView } from "./GameView";
 export { GraphicsOverridesSchema } from "./GraphicsOverrides";
 export type { GraphicsOverrides } from "./GraphicsOverrides";
+export { preloadAtlasData } from "./passes/name-pass/AtlasData";
 export type { SpawnCenter } from "./passes/SpawnOverlayPass";
 export {
   applyDarkModeOverride,

src/client/render/gl/passes/name-pass/AtlasData.ts

@@ -4,7 +4,7 @@
  */
 
 import emojiAtlasMeta from "resources/atlases/emoji-atlas-meta.json";
-import atlasData from "resources/atlases/msdf-atlas.json";
+import { assetUrl } from "src/core/AssetUrls";
 import type { BMChar, BMKerning, ParsedAtlas } from "./Types";
 import { CHAR_RANGE } from "./Types";
 
@@ -12,15 +12,45 @@ import { CHAR_RANGE } from "./Types";
 // Atlas parsing
 // ---------------------------------------------------------------------------
 
+interface RawMsdfAtlas {
+  info: { size: number };
+  common: { base: number; scaleW: number; scaleH: number };
+  distanceField?: { distanceRange: number };
+  chars: BMChar[];
+  kernings?: BMKerning[];
+}
+
+// Fetched at game-load time rather than statically imported — the JSON is
+// ~320 KB minified and would otherwise sit in the main bundle.
+let atlasData: RawMsdfAtlas | null = null;
+let atlasDataPromise: Promise<void> | null = null;
+
+export function preloadAtlasData(): Promise<void> {
+  atlasDataPromise ??= fetch(assetUrl("atlases/msdf-atlas.json"))
+    .then((response) => {
+      if (!response.ok) {
+        throw new Error(`Failed to fetch msdf-atlas.json: ${response.status}`);
+      }
+      return response.json();
+    })
+    .then((json) => {
+      atlasData = json as RawMsdfAtlas;
+    });
+  return atlasDataPromise;
+}
+
 export function parseAtlasData(): ParsedAtlas {
+  if (atlasData === null) {
+    throw new Error("Atlas data not loaded; await preloadAtlasData() first");
+  }
   return {
     fontSize: atlasData.info.size,
     base: atlasData.common.base,
     scaleW: atlasData.common.scaleW,
     scaleH: atlasData.common.scaleH,
-    distanceRange: (atlasData as any).distanceField?.distanceRange ?? 4,
-    chars: atlasData.chars as BMChar[],
-    kernings: (atlasData.kernings ?? []) as BMKerning[],
+    distanceRange: atlasData.distanceField?.distanceRange ?? 4,
+    chars: atlasData.chars,
+    kernings: atlasData.kernings ?? [],
   };
 }