ISMIS Helper: cross-browser build, CI, PDF fixes, Chrome download fix

Squash merge of feat/ismis-helper into prod.

background.js

@@ -0,0 +1,78 @@
+'use strict';
+// Cross-browser API namespace. Firefox provides Promise-based `browser.*`;
+// Chrome MV3 exposes `browser.*` too, but some builds only populate the
+// `chrome.*` global. Alias to whichever is present.
+if (typeof browser === 'undefined' || browser == null) {
+  var browser = (typeof chrome !== 'undefined' ? chrome : {});
+}
+
+function errMsg(err) {
+  return String((err && err.message) || err);
+}
+
+// Build a download URL from PDF bytes. Chrome MV3 runs the background as a
+// service worker, where URL.createObjectURL is NOT available, so we use a
+// base64 data URL (works in both Firefox and Chrome). PDFs here are small
+// (~150KB), well within data-URL length limits.
+function pdfDataUrl(bytes) {
+  let binary = '';
+  const chunk = 0x8000;
+  for (let i = 0; i < bytes.length; i += chunk) {
+    binary += String.fromCharCode.apply(null, bytes.subarray(i, i + chunk));
+  }
+  return 'data:application/pdf;base64,' + btoa(binary);
+}
+
+browser.runtime.onMessage.addListener((msg, sender, sendResponse) => {
+  if (msg && msg.type === 'generate-pdf') {
+    generatePdf(msg.data)
+      .then(() => sendResponse({ ok: true }))
+      .catch((err) => sendResponse({ ok: false, error: errMsg(err) }));
+    return true;
+  }
+});
+
+function formatPeriod(period) {
+  if (!period) return '';
+  return String(period)
+    .replace(/\b1ST\b/g, '1st')
+    .replace(/\b2ND\b/g, '2nd')
+    .replace(/\b3RD\b/g, '3rd')
+    .replace(/\b(\d+)TH\b/g, '$1th')
+    .toLowerCase()
+    .replace(/^./, (c) => c.toUpperCase());
+}
+
+async function generatePdf(data) {
+  const bytes = await ISMIStools.buildStudyLoadPdf(data);
+  // Chrome MV3 background is a service worker (no URL.createObjectURL), so we
+  // use a base64 data URL that works in both browsers.
+  const url = pdfDataUrl(bytes);
+  const header = data.header || {};
+  const year = parseInt(data.year, 10);
+  const period = formatPeriod(data.period || header.semester || '');
+  const compactProgram = ISMIStools.compactProgram(header.program || '');
+  const schoolYear = Number.isFinite(year) ? `${year}-${year + 1}` : '';
+  const parts = [
+    header.studentId || (header.fullName ? header.fullName.replace(/\s+/g, ' ') : ''),
+    compactProgram,
+    schoolYear ? 'S.Y. ' + schoolYear : '',
+    period,
+    'Study Load'
+  ].filter(Boolean);
+  const filename = parts.join(' - ') + '.pdf';
+  const fallback = 'Study Load - ' + (header.fullName || 'Student') + '.pdf';
+  const safeFilename = filename || fallback;
+
+  try {
+    const id = await browser.downloads.download({ url, filename: safeFilename, saveAs: true });
+    const onChanged = (delta) => {
+      if (delta.id === id && delta.state && (delta.state.current === 'complete' || delta.state.current === 'interrupted')) {
+        browser.downloads.onChanged.removeListener(onChanged);
+      }
+    };
+    browser.downloads.onChanged.addListener(onChanged);
+  } catch (err) {
+    throw err;
+  }
+}