Add average grade display and Fix CORS violation

Add average grade display and also fix the CORS violation caused by pdfjs trying to load PDFs from URLs that Firefox extensions can't access.

fixed by instead:
- Fetching the PDF as an ArrayBuffer directly from the URL
- Passing the ArrayBuffer to pdfjs using { data: arrayBuffer } instead of passing a URL

src/plugins/built-in/assessmentsAverage/index.ts

@@ -125,10 +125,12 @@ const assessmentsAveragePlugin: Plugin<typeof settings, weightingsStorage> = {
       );
       if (!assessmentsList) return;
 
-      const gradeElements = document.querySelectorAll(
-        "[class*='Thermoscore__text___']",
-      );
-      if (!gradeElements.length) return;
+      // Get marks from React state to match with DOM elements
+      const state = await ReactFiber.find(
+        "[class*='AssessmentList__items___']",
+      ).getState();
+      const marks = state["marks"];
+      if (!marks || !marks.length) return;
 
       // Parse and average grades
       const letterToNumber: Record<string, number> = {
@@ -162,19 +164,59 @@ const assessmentsAveragePlugin: Plugin<typeof settings, weightingsStorage> = {
         return letterToNumber[str] ?? 0;
       }
 
-      let total = 0;
+      // Get all assessment items (excluding the average we might have added)
+      const assessmentItems = Array.from(
+        assessmentsList.querySelectorAll(`[class*='AssessmentItem__AssessmentItem___']`),
+      ).filter(
+        (item) =>
+          !item.querySelector(`[class*='AssessmentItem__title___']`)?.textContent?.includes("Subject Average"),
+      );
+
+      // Match marks to assessment items and calculate weighted average
+      let weightedTotal = 0;
+      let totalWeight = 0;
+      let hasInaccurateWeighting = false;
       let count = 0;
-      gradeElements.forEach((el) => {
-        const grade = parseGrade(el.textContent || "");
-        if (grade > 0) {
-          total += grade;
-          count++;
+
+      for (let i = 0; i < marks.length && i < assessmentItems.length; i++) {
+        const mark = marks[i];
+        const assessmentItem = assessmentItems[i];
+        const gradeElement = assessmentItem.querySelector(
+          `[class*='Thermoscore__text___']`,
+        );
+
+        if (!gradeElement) continue;
+
+        const grade = parseGrade(gradeElement.textContent || "");
+        if (grade <= 0) continue;
+
+        const assessmentID = String(mark.id);
+        const weighting = api.storage.weightings[assessmentID];
+
+        // Check if weighting is unavailable or still processing
+        if (!weighting || weighting === "N/A" || weighting === "processing") {
+          hasInaccurateWeighting = true;
+          // Fall back to equal weighting if unavailable
+          weightedTotal += grade;
+          totalWeight += 1;
+        } else {
+          const weight = parseFloat(weighting);
+          if (!isNaN(weight) && weight > 0) {
+            weightedTotal += grade * weight;
+            totalWeight += weight;
+          } else {
+            // Invalid weight, use equal weighting
+            weightedTotal += grade;
+            totalWeight += 1;
+            hasInaccurateWeighting = true;
+          }
         }
-      });
+        count++;
+      }
 
-      if (!count) return;
+      if (!count || totalWeight === 0) return;
 
-      const avg = total / count;
+      const avg = weightedTotal / totalWeight;
       const rounded = Math.ceil(avg / 5) * 5;
       const numberToLetter = Object.entries(letterToNumber).reduce(
         (acc, [k, v]) => {
@@ -195,6 +237,16 @@ const assessmentsAveragePlugin: Plugin<typeof settings, weightingsStorage> = {
       );
       if (existing?.textContent === "Subject Average") return;
 
+      // Build warning message if needed
+      let warningHTML = "";
+      if (hasInaccurateWeighting) {
+        warningHTML = /* html */ `
+          <div style="margin-top: 4px; font-size: 11px; color: rgba(255, 255, 255, 0.6); opacity: 0.8; line-height: 1.3;">
+            ⚠ Some weightings unavailable
+          </div>
+        `;
+      }
+
       // Use the dynamic class names in the HTML template
       const averageElement = stringToHTML(/* html */ `
         <div class="${assessmentItemClass}">
@@ -202,12 +254,13 @@ const assessmentsAveragePlugin: Plugin<typeof settings, weightingsStorage> = {
             <div class="${metaClass}">
               <div class="${simpleResultClass}">
                 <div class="${titleClass}">Subject Average</div>
+                ${warningHTML}
               </div>
             </div>
           </div>
           <div class="${thermoscoreClass}">
             <div class="${fillClass}" style="width: ${avg.toFixed(2)}%">
-              <div class="${textClass}" title="${display}">${display}</div>
+              <div class="${textClass}" title="${hasInaccurateWeighting ? display + ' (some weightings unavailable)' : display}">${display}</div>
             </div>
           </div>
         </div>
@@ -219,7 +272,11 @@ const assessmentsAveragePlugin: Plugin<typeof settings, weightingsStorage> = {
 };
 
 async function extractPDFText(url: string): Promise<string> {
-  const loadingTask = pdfjs.getDocument(url);
+  // Fetch PDF as ArrayBuffer to avoid blob URL CSP issues in Firefox extensions
+  const response = await fetch(url);
+  const arrayBuffer = await response.arrayBuffer();
+  
+  const loadingTask = pdfjs.getDocument({ data: arrayBuffer });
   const pdf = await loadingTask.promise;
 
   let text = "";