feat(progress): live status bar + % complete during exports

Adds a progress bar below the export buttons showing the current step
(reading table, fetching course descriptions i/N, profile, year level,
building file) with a 0-100% fill. Threads an onProgress callback through
scrapeStudyLoad and resolveYearLevel. Buttons disable during export to
prevent double-triggers; bar clears ~3s after success.

content.js

@@ -94,9 +94,10 @@
     return m ? m[1] : '';
   }
 
-  async function scrapeStudyLoad() {
+  async function scrapeStudyLoad(onProgress) {
     const table = document.querySelector('table.table-forum');
     if (!table) throw new Error('No study load table found on this page.');
+    if (onProgress) onProgress('Reading study load table', 5);
     const courses = ISMIStools.parseStudyLoadTable(table.outerHTML);
     if (!courses.length) throw new Error('No courses found in study load table.');
 
@@ -117,16 +118,21 @@
 
     const uniqueCodes = [...new Set(courses.map((c) => c.courseCode))];
     const descMap = {};
-    for (const code of uniqueCodes) {
+    if (onProgress && uniqueCodes.length) onProgress('Fetching course descriptions (0/' + uniqueCodes.length + ')', 10);
+    for (let i = 0; i < uniqueCodes.length; i++) {
+      const code = uniqueCodes[i];
       try {
         descMap[code] = await fetchCourseDescription(code, academicPeriod, academicYear, token);
       } catch (e) {
         descMap[code] = '';
       }
+      if (onProgress) onProgress('Fetching course descriptions (' + (i + 1) + '/' + uniqueCodes.length + ')',
+        10 + 60 * ((i + 1) / uniqueCodes.length));
     }
     courses.forEach((c) => { c.description = descMap[c.courseCode] || ''; });
 
     let header = {};
+    if (onProgress) onProgress('Reading profile', 75);
     try {
       const resp = await fetch('/Manage/Student', { credentials: 'same-origin' });
       if (!resp.ok) throw new Error('Profile request failed: ' + resp.status);
@@ -144,7 +150,7 @@
     // Resolve the Year Level for the PRINTED semester (hybrid, see design
     // spec): custom setting wins; else View Grades history matching; else the
     // units math; else the profile-scraped value.
-    header.yearLevel = await resolveYearLevel(header, selectedPeriod, selectedYear);
+    header.yearLevel = await resolveYearLevel(header, selectedPeriod, selectedYear, onProgress);
 
     return { header, courses, period: selectedPeriod, year: selectedYear };
   }
@@ -163,7 +169,7 @@
   // Hybrid year-level resolution. Returns null only if every source failed.
   // mode: 'auto' (default) runs the full hybrid; 'custom' uses only the custom
   // value; 'off' uses only the profile-scraped value.
-  async function resolveYearLevel(header, period, year) {
+  async function resolveYearLevel(header, period, year, onProgress) {
     const settings = await browser.storage.local.get(['yearMode', 'customYearLevel']);
     const mode = settings.yearMode || 'auto';
     const custom = String(settings.customYearLevel || '').trim();
@@ -183,10 +189,12 @@
     //    total prospectus units minus still-lacking units. This reflects real
     //    earned units and is correct even for students who repeated or failed
     //    a year (the naive grade-history count would over-advance them).
+    if (onProgress) onProgress('Determining year level', 80);
     const [prospectusHtml, lackingHtml] = await Promise.all([
       fetchText('/prospectus/StudentProspectus'),
       fetchText('/Extras/ViewLackingSubjectsStudent1')
     ]);
+    if (onProgress) onProgress('Checking remaining units', 88);
     if (prospectusHtml) {
       const yearUnits = ISMIStools.parseProspectusYearUnits(prospectusHtml);
       const lacking = lackingHtml ? ISMIStools.parseLackingSubjectsUnits(lackingHtml) : 0;
@@ -197,6 +205,7 @@
     // 2. GRADE HISTORY — fallback only when the units path is unavailable.
     //    It counts distinct academic years, so it is only an approximation for
     //    the printed semester and is not used when units data is present.
+    if (onProgress) onProgress('Checking grade history', 93);
     const gradesHtml = await fetchText('/ViewGrades');
     if (gradesHtml) {
       const history = ISMIStools.parseGradeHistory(gradesHtml);
@@ -231,26 +240,34 @@
 
   async function onDownloadPdf() {
     const btn = document.getElementById(BTN_ID);
+    setExportButtonsDisabled(true);
     try {
       btn.disabled = true;
       btn.innerHTML = '<i class="fa fa-spinner fa-spin"></i> Downloading...';
-      const { header, courses } = await scrapeStudyLoad();
+      setProgress('Reading study load', 2);
+      const { header, courses } = await scrapeStudyLoad((l, p) => setProgress(l, p));
       const included = ISMIStools.filterStudyLoadCourses(courses);
       if (!included.length) throw new Error('No enrolled courses found.');
       const totalUnits = ISMIStools.sumUnits(included);
       const settings = await browser.storage.local.get(['truncateDescription', 'showYearLevel']);
       header.showYearLevel = settings.showYearLevel !== false;
+      setProgress('Building PDF', 95);
       const res = await browser.runtime.sendMessage({
         type: 'generate-pdf',
         data: { header, courses: included, totalUnits, truncateDescription: settings.truncateDescription !== false }
       });
       if (!res || !res.ok) throw new Error((res && res.error) || 'PDF generation failed');
+      setProgress('Done ✓', 100);
       showToast('PDF downloaded.');
+      setTimeout(clearProgress, 3000);
     } catch (err) {
+      setProgress('Error: ' + ((err && err.message) || err), 100);
       showToast('Error: ' + ((err && err.message) || err), true);
     } finally {
+      setExportButtonsDisabled(false);
       btn.disabled = false;
       btn.innerHTML = '<i class="fa fa-download"></i> Download PDF';
+      setTimeout(clearProgress, 4000);
     }
   }
 
@@ -258,20 +275,29 @@
   // every format gets the same header/courses/totalUnits payload and the same
   // hybrid year-level resolution.
   async function onExport(format) {
+    setExportButtonsDisabled(true);
     try {
-      const { header, courses, period, year } = await scrapeStudyLoad();
+      setProgress('Reading ' + format.toUpperCase() + ' data', 2);
+      const { header, courses, period, year } = await scrapeStudyLoad((l, p) => setProgress(l, p));
       const included = ISMIStools.filterStudyLoadCourses(courses);
       if (!included.length) throw new Error('No enrolled courses found.');
       const totalUnits = ISMIStools.sumUnits(included);
+      setProgress('Building ' + format.toUpperCase() + ' file', 95);
       const res = await browser.runtime.sendMessage({
         type: 'export',
         format,
         data: { header, courses: included, totalUnits, period, year }
       });
       if (!res || !res.ok) throw new Error((res && res.error) || 'Export failed');
+      setProgress('Done ✓', 100);
       showToast('Exported ' + format.toUpperCase() + '.');
+      setTimeout(clearProgress, 3000);
     } catch (err) {
+      setProgress('Error: ' + ((err && err.message) || err), 100);
       showToast('Error: ' + ((err && err.message) || err), true);
+      setTimeout(clearProgress, 4000);
+    } finally {
+      setExportButtonsDisabled(false);
     }
   }
 
@@ -286,6 +312,76 @@
     return b;
   }
 
+  // Disable/enable all export buttons (incl. PDF) to prevent double-triggers.
+  function setExportButtonsDisabled(disabled) {
+    const ids = [BTN_ID, 'ismisHelperExportCsvBtn', 'ismisHelperExportXlsxBtn',
+      'ismisHelperExportJsonBtn', 'ismisHelperExportNextUpBtn'];
+    for (const id of ids) {
+      const b = document.getElementById(id);
+      if (b) b.disabled = disabled;
+    }
+  }
+
+  // ---- Export progress indicator ----
+  const PROGRESS_ID = 'ismisHelperProgress';
+  const PROGRESS_FILL_ID = 'ismisHelperProgressFill';
+  const PROGRESS_LABEL_ID = 'ismisHelperProgressLabel';
+  let progressEl = null;
+
+  // Set the status bar label + width (0-100). With no percent, shows just text.
+  function setProgress(label, percent) {
+    if (!progressEl) progressEl = document.getElementById(PROGRESS_ID);
+    if (!progressEl) return;
+    progressEl.style.display = 'flex';
+    const fill = document.getElementById(PROGRESS_FILL_ID);
+    if (fill) fill.style.width = Math.max(0, Math.min(100, percent)) + '%';
+    const lab = document.getElementById(PROGRESS_LABEL_ID);
+    if (lab) lab.textContent = label;
+  }
+
+  function clearProgress() {
+    if (!progressEl) progressEl = document.getElementById(PROGRESS_ID);
+    if (!progressEl) return;
+    progressEl.style.display = 'none';
+    const fill = document.getElementById(PROGRESS_FILL_ID);
+    if (fill) fill.style.width = '0%';
+  }
+
+  function makeProgressEl() {
+    if (document.getElementById(PROGRESS_ID)) return;
+    const el = document.createElement('div');
+    el.id = PROGRESS_ID;
+    el.style.display = 'none';
+    el.style.alignItems = 'center';
+    el.style.gap = '10px';
+    el.style.margin = '8px 0';
+    el.style.fontSize = '12px';
+    el.style.color = '#555';
+    el.style.width = '100%';
+
+    const track = document.createElement('div');
+    track.style.flex = '1';
+    track.style.height = '8px';
+    track.style.background = '#e2e2e2';
+    track.style.borderRadius = '4px';
+    track.style.overflow = 'hidden';
+    const fill = document.createElement('div');
+    fill.id = PROGRESS_FILL_ID;
+    fill.style.width = '0%';
+    fill.style.height = '100%';
+    fill.style.background = '#28a745';
+    fill.style.transition = 'width .2s ease';
+    track.appendChild(fill);
+
+    const lab = document.createElement('span');
+    lab.id = PROGRESS_LABEL_ID;
+    lab.style.whiteSpace = 'nowrap';
+
+    el.appendChild(track);
+    el.appendChild(lab);
+    return el;
+  }
+
   function injectDownloadButton() {
     if (document.getElementById(BTN_ID)) return;
     const unitsP = findTotalUnitsP();
@@ -320,6 +416,7 @@
 
     unitsP.parentNode.insertBefore(wrapper, unitsP);
     wrapper.appendChild(btnGroup);
+    wrapper.appendChild(makeProgressEl());
     wrapper.appendChild(unitsP);
   }