Initial skills documentation — 25 categories, all SKILL.md + references + scripts

skills/delegation-pattern/references/cascade-failure-debugging.md

@@ -0,0 +1,42 @@
+# Silent Cascade Failure — JS TypeError Kills Async Operations
+
+## Pattern (discovered Jul 12, 2026)
+
+A single `TypeError` (e.g. `.classList.add()` on a `null` element) in early synchronous inline script kills ALL subsequent code — including `fetch()` calls that would load nav, content, or UI elements.
+
+The symptom surface is confusing: blank page, no menu, no content, no visible error.
+
+## Example
+
+```javascript
+// WRONG — crashes before nav fetch runs
+if (Ops.isAuthenticated()) {
+    overlay.classList.remove('show');
+    document.getElementById('logoutBtn').classList.add('show');  // TypeError if nav not loaded
+    loadContent();  // Never runs
+}
+fetch('/nav.html').then(...)  // Never runs either
+```
+
+## Fix pattern
+
+Always guard DOM lookups that depend on async-loaded content:
+
+```javascript
+// Wait for async content before accessing
+var wait = setInterval(function() {
+    var el = document.getElementById('logoutBtn');
+    if (el) {
+        el.classList.add('show');
+        clearInterval(wait);
+        loadContent();
+    }
+}, 100);
+```
+
+## Prevention checklist
+
+- [ ] Every `getElementById()` call is guarded (especially elements from fetched templates)
+- [ ] Auth logic does NOT touch DOM elements from separate fetches
+- [ ] `fetch()` / `setInterval()` are NOT placed after unguarded DOM access
+- [ ] Inline scripts tolerate missing elements without crashing