fix(grabcraft): support external JS files for voxel data extraction

GrabCraft moved myRenderObject data from inline scripts to external JS
files (/js/RenderObject/myRenderObject_XXXX.js). This adds extraction of
the external script URL, fetching and parsing the nested JSON object, with
fallback to the original inline extraction for legacy pages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/grabcraft.js

@@ -125,7 +125,21 @@ export async function fetchBlueprint(url) {
     : 'Unknown Blueprint';
 
   // Extract render object (3D voxel data)
-  const voxels = extractRenderObject(html);
+  // Try external JS file first (new GrabCraft format), then fall back to inline extraction
+  let voxels = [];
+  const externalScript = extractExternalScriptUrl(html);
+  if (externalScript) {
+    try {
+      log(TAG, `Fetching external voxel data: ${externalScript.url}`);
+      const jsContent = await fetchPage(externalScript.url);
+      voxels = parseExternalRenderObject(jsContent);
+    } catch (err) {
+      logError(TAG, `Failed to fetch external JS: ${err.message}`);
+    }
+  }
+  if (voxels.length === 0) {
+    voxels = extractRenderObject(html); // fallback for legacy pages
+  }
 
   // Extract materials list
   const materials = extractMaterials(html);
@@ -302,6 +316,76 @@ function extractRenderObject(html) {
   return voxels;
 }
 
+/**
+ * Extract URL of external myRenderObject JS file from the page HTML.
+ * GrabCraft now loads voxel data from e.g. /js/RenderObject/myRenderObject_1234.js
+ * @param {string} html
+ * @returns {{ url: string, blueprintId: string } | null}
+ */
+function extractExternalScriptUrl(html) {
+  const regex = /<script[^>]+src=["']((?:https?:\/\/[^"']*)?\/js\/RenderObject\/myRenderObject_(\d+)\.js)["']/i;
+  const match = html.match(regex);
+  if (!match) return null;
+
+  let url = match[1];
+  if (url.startsWith('/')) {
+    url = GRABCRAFT_BASE + url;
+  }
+  return { url, blueprintId: match[2] };
+}
+
+/**
+ * Parse a nested myRenderObject from an external JS file.
+ * Expected format: var myRenderObject = { y: { x: { z: { mat_id, hex, name, ... } } } };
+ * @param {string} jsContent - Raw JS file content
+ * @returns {Array<{ x: number, y: number, z: number, matId: string, hex: string|null, matName: string|null }>}
+ */
+function parseExternalRenderObject(jsContent) {
+  const voxels = [];
+
+  // Strip "var myRenderObject = " prefix and trailing ";"
+  const stripped = jsContent
+    .replace(/^\s*var\s+myRenderObject\s*=\s*/, '')
+    .replace(/;\s*$/, '')
+    .trim();
+
+  let obj;
+  try {
+    obj = JSON.parse(stripped);
+  } catch {
+    logError(TAG, 'Failed to JSON.parse external myRenderObject');
+    return voxels;
+  }
+
+  if (typeof obj !== 'object' || obj === null) return voxels;
+
+  for (const [yKey, yVal] of Object.entries(obj)) {
+    const y = parseInt(yKey, 10);
+    if (isNaN(y) || typeof yVal !== 'object' || yVal === null) continue;
+
+    for (const [xKey, xVal] of Object.entries(yVal)) {
+      const x = parseInt(xKey, 10);
+      if (isNaN(x) || typeof xVal !== 'object' || xVal === null) continue;
+
+      for (const [zKey, entry] of Object.entries(xVal)) {
+        const z = parseInt(zKey, 10);
+        if (isNaN(z) || typeof entry !== 'object' || entry === null) continue;
+
+        voxels.push({
+          x,
+          y,
+          z,
+          matId: String(entry.mat_id || '0'),
+          hex: entry.hex || null,
+          matName: entry.name || null,
+        });
+      }
+    }
+  }
+
+  return voxels;
+}
+
 /**
  * Extract materials list from Highcharts series data.
  * GrabCraft pages include chart data like:
@@ -351,10 +435,13 @@ function extractMaterials(html) {
  * @returns {Promise<string>} HTML content
  */
 async function fetchPage(url) {
+  const isJs = url.endsWith('.js');
   const response = await fetch(url, {
     headers: {
       'User-Agent': USER_AGENT,
-      'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
+      'Accept': isJs
+        ? 'application/javascript, */*;q=0.8'
+        : 'text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
       'Accept-Language': 'en-US,en;q=0.5',
     },
   });