Add scroll depth tracking

static/assets/js/umami-helper.js

@@ -0,0 +1,28 @@
+// Umami: safe track (no-op if script blocked or not loaded)
+function umamiTrack(name, data) {
+    if (
+        typeof window.umami !== 'undefined' &&
+        typeof window.umami.track === 'function'
+    ) {
+        if (data != null) window.umami.track(name, data);
+        else window.umami.track(name);
+    }
+}
+
+// Umami: scroll depth (25%, 50%, 75%, 100%) – once per milestone
+const scrollMilestones = new Set();
+function onScroll() {
+    const doc = document.documentElement;
+    const scrollTop = doc.scrollTop || document.body.scrollTop;
+    const scrollHeight =
+        (doc.scrollHeight || document.body.scrollHeight) - window.innerHeight;
+    if (scrollHeight <= 0) return;
+    const pct = Math.round((scrollTop / scrollHeight) * 100);
+    for (const m of [25, 50, 75, 100]) {
+        if (pct >= m && !scrollMilestones.has(m)) {
+            scrollMilestones.add(m);
+            umamiTrack('scroll-depth', { depth: String(m) });
+        }
+    }
+}
+window.addEventListener('scroll', onScroll, { passive: true });