fix(core): auto-detect three.js asset readiness via adapter contract (#1543)

Replaces the original `window.__hyperframesReady` authored API with an internal adapter contract: `RuntimeDeterministicAdapter.getReadyPromise?: () => PromiseLike | null`. The Three.js adapter implements it by hooking `THREE.DefaultLoadingManager.onStart/onLoad`; the runtime collects promises from every adapter and gates `window.__renderReady = true` on them. Zero authoring burden — composition authors write plain Three.js, framework handles async asset gating automatically.

Also keeps the orthogonal `htmlDocument.ts` script-stripping refactor (substring → regex for simple flag assignments), which fixes the bug where authored scripts referencing readiness flags were stripped despite never assigning them.

Stamped by Magi and Miguel; CI green; tests 33/33 pass.

packages/core/src/compiler/htmlDocument.ts

@@ -13,9 +13,13 @@ const RUNTIME_INLINE_MARKERS = [
   "__hyperframeRuntimeBootstrapped",
   "__hyperframeRuntime",
   "__hyperframeRuntimeTeardown",
+  "__HF_EXPORT_RENDER_SEEK_CONFIG",
   "window.__player =",
-  "window.__playerReady",
-  "window.__renderReady",
+];
+
+const SIMPLE_RUNTIME_FLAG_ASSIGNMENTS = [
+  /^window\.__playerReady\s*=\s*(?:true|false)\s*;?$/,
+  /^window\.__renderReady\s*=\s*(?:true|false)\s*;?$/,
 ];
 
 /**
@@ -115,9 +119,22 @@ function shouldStripRuntimeScriptBlock(block: string): boolean {
   for (const marker of RUNTIME_INLINE_MARKERS) {
     if (block.includes(marker)) return true;
   }
+  const scriptSource = getScriptSource(block).trim();
+  for (const pattern of SIMPLE_RUNTIME_FLAG_ASSIGNMENTS) {
+    if (pattern.test(scriptSource)) return true;
+  }
   return false;
 }
 
+function getScriptSource(block: string): string {
+  const startTagEnd = findTagEnd(block, 1);
+  if (startTagEnd === -1) return "";
+  const loweredBlock = block.toLowerCase();
+  const closeTagStart = loweredBlock.lastIndexOf("</script");
+  const end = closeTagStart === -1 ? block.length : closeTagStart;
+  return block.slice(startTagEnd + 1, end);
+}
+
 function isTagBoundary(char: string): boolean {
   return char === "" || char === ">" || char === "/" || isHtmlWhitespace(char);
 }