Faster first load; demo date tags stay current

First load:
- Draw the Overview as soon as the data arrives instead of on its next
  2-second timer tick (about 2.5 s to 0.6 s on a typical connection).
- Start on DOMContentLoaded instead of window.onload.
- Load the ~900 KB PDF library only when someone exports a PDF.
- Fetch the startup files side by side, and build the docs search index
  after the dashboard has drawn (unless the visit starts on /docs).
- Show a loading placeholder on the Overview until the data arrives.

Demo: the date-batch tags sit on fixed working-day offsets from today.
The seed records them in Demo-Dates.json and the worker relabels them when
the day changes, so a long-running container never looks stale.

web/index.html

@@ -8,7 +8,6 @@
     <link rel="icon" href="/favicon.png" type="image/png">
 
     <script src="/vendor/marked/marked.min.js"></script>
-    <script src="/vendor/html2pdf/html2pdf.bundle.min.js"></script>
     <link rel="stylesheet" href="/vendor/highlight/styles/atom-one-dark.min.css">
     <script src="/vendor/highlight/highlight.min.js"></script>
     <script src="/vendor/highlight/languages/powershell.min.js"></script>
@@ -1784,7 +1783,22 @@
             }
         }
 
-        window.onload = async () => {
+        // PDF export library (~900 KB): fetched the first time someone exports, not on every visit
+        function loadHtml2Pdf() {
+            if (window.html2pdf) return Promise.resolve();
+            return window._html2pdfLoading || (window._html2pdfLoading = new Promise((resolve, reject) => {
+                const s = document.createElement('script');
+                s.src = '/vendor/html2pdf/html2pdf.bundle.min.js';
+                s.onload = resolve;
+                s.onerror = () => { window._html2pdfLoading = null; reject(new Error('Could not load the PDF library')); };
+                document.head.appendChild(s);
+            }));
+        }
+
+        // Start as soon as the page is parsed (not after every image and script has finished, as
+        // window.onload would); the timeout lets every module's own DOMContentLoaded setup run first
+        document.addEventListener('DOMContentLoaded', () => setTimeout(initDashboard, 0));
+        async function initDashboard() {
             updateThemeBtn();
             initMasterTables();
 
@@ -1812,9 +1826,9 @@
             document.getElementById('btn-edit-mode').innerHTML = EDIT_SVG;
             document.getElementById('btn-save-doc').innerHTML = `${SAVE_SVG} Save`;
             
-            await loadBlacklist();
-            await loadDocsList();
-            await loadAllTags();
+            // Load side by side; the device data doesn't wait for the article list
+            const docsReady = loadDocsList();
+            await Promise.all([loadBlacklist(), loadAllTags()]);
             
             const savedTech = localStorage.getItem('usmt_tech_id');
             if (savedTech) {
@@ -1822,15 +1836,16 @@
                 await loadTechRoster();
             }
 
+            startDashboard();
+
             // Check if we were opened in a new tab specifically to view a document
+            await docsReady;
             const urlParams = new URLSearchParams(window.location.search);
             const targetDoc = urlParams.get('doc');
             if (targetDoc && availableDocs.includes(targetDoc)) {
                 await openDoc(targetDoc);
             }
-            
-            startDashboard();
-        };
+        }
 
         // Code spans and fenced blocks are set aside while the [[Badge:..]] / [[Copy:..]] / UNC
         // path rewrites run, so an article can show that syntax literally inside `code`
@@ -2088,7 +2103,7 @@
             btn.disabled = true;
             btn.innerHTML = btn.innerHTML.replace('PDF', 'Exporting...');
 
-            html2pdf().set(opt).from(clone).save().finally(() => {
+            loadHtml2Pdf().then(() => html2pdf().set(opt).from(clone).save()).finally(() => {
                 btn.disabled = false;
                 btn.innerHTML = btn.innerHTML.replace('Exporting...', 'PDF');
             });
@@ -4307,7 +4322,8 @@
 
         async function pullData() {
             try {
-                // 1. FAST STATE POLLING
+                // 1. FAST STATE POLLING (the tracked list is fetched alongside it)
+                const trackFetch = fetch('Tracked-Devices.json?t=' + Date.now()).catch(() => null);
                 const stateRes = await fetch('Worker-State.json?t=' + Date.now());
                 if (!stateRes.ok) return;
                 const state = await stateRes.json();
@@ -4353,7 +4369,7 @@
                 document.getElementById('syncBreakdown').innerHTML = DeviceInfo.syncBreakdownHtml(state);
 
                 // Check if Tracked-Devices was updated by you or a teammate
-                const trackRes = await fetch('Tracked-Devices.json?t=' + Date.now()).catch(() => null);
+                const trackRes = await trackFetch;
                 let currentTrackedHash = "";
                 let trackData = null;
                 if (trackRes && trackRes.ok) {
@@ -4374,6 +4390,7 @@
                 globalTrackedHash = currentTrackedHash; 
 
                 // 2. FETCH CORE DATA AND ADVANCED DATA
+                const advFetch = fetch('Advanced-Cache.json?t=' + Date.now()).catch(() => null);
                 const dataRes = await fetch('Data.json?t=' + Date.now()).catch(() => null);
                 if (dataRes && dataRes.ok) {
                     const payload = await dataRes.json();
@@ -4387,7 +4404,7 @@
                     }
                 }
 
-                const advRes = await fetch('Advanced-Cache.json?t=' + Date.now()).catch(() => null);
+                const advRes = await advFetch;
                 if (advRes && advRes.ok) {
                     advancedDataCache = await advRes.json();
                 }
@@ -4496,6 +4513,8 @@
                 renderSoftwareTable(); // <-- Forces the Software tab to update instantly!
                 renderCustomTable();
                 refreshOpenDialogs();
+                document.dispatchEvent(new Event('usmt:data'));
+                if (window.Overview) Overview.refresh();   // draw the Overview now, not on its next timer tick
 
                 // 3. LAZY LOAD SOFTWARE LAST
                 fetch('Software-Cache.json?t=' + Date.now())
@@ -4528,6 +4547,7 @@
                                 renderSoftwareTable();
                                 renderCustomTable();
                                 refreshOpenDialogs(true);
+                                if (window.Overview) Overview.refresh();
                             }
                         }
                     }).catch(() => null);