Fix setDur implicit event, title XSS, hardcoded pulse URL, suppress error toast

- suppressions.html: setDur() now takes explicit element param instead of relying
  on implicit global event.target (which fails outside direct click handlers)
- suppressions.html: removeSuppression() now shows error toast on failed DELETE
- templates/index.html: escape description in title attribute with |e filter
  to prevent attribute breakout on quotes in description text
- diagnose.py: derive Pulse execution URL from pulse_client.url instead of
  hardcoding http://pulse.lotusguild.org

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

templates/suppressions.html

@@ -180,10 +180,10 @@
     document.getElementById('s-name').required = (t!=='all');
   }
 
-  function setDur(mins) {
+  function setDur(mins, el) {
     document.getElementById('s-expires').value = mins || '';
     document.querySelectorAll('.duration-pills .pill').forEach(p => p.classList.remove('active'));
-    event.target.classList.add('active');
+    if (el) el.classList.add('active');
     const hint = document.getElementById('s-dur-hint');
     if (mins) {
       const h = Math.floor(mins/60), m = mins%60;
@@ -224,6 +224,8 @@
     if (data.success) {
       document.getElementById(`sup-row-${id}`)?.remove();
       showToast('Suppression removed', 'success');
+    } else {
+      showToast(data.error || 'Failed to remove suppression', 'error');
     }
   }
 </script>