Fix push notifications: focus suppression, empty body, error visibility

- sw.js: suppress notification when the target chat tab is already focused
  (clients.matchAll visibility check before showNotification)
- generation_task.py: provide meaningful body for tool-only responses
  (lists tool names instead of sending an empty string that browsers discard);
  promote scheduling failure from debug to warning
- push.py: promote send errors from warning to error with exc_info;
  log successful sends at INFO so they're visible in normal operation

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

frontend/public/sw.js

@@ -2,12 +2,22 @@
 self.addEventListener('push', event => {
   if (!event.data) return;
   const data = event.data.json();
+  const notifUrl = data.url || '/';
+
   event.waitUntil(
-    self.registration.showNotification(data.title || 'Fabled Assistant', {
+    clients.matchAll({ type: 'window', includeUncontrolled: true }).then(clientList => {
+      // Suppress notification if the user already has the relevant page focused
+      for (const client of clientList) {
+        if (client.visibilityState === 'visible' && client.url.includes(notifUrl)) {
+          return;
+        }
+      }
+      return self.registration.showNotification(data.title || 'Fabled Assistant', {
         body: data.body || '',
         icon: '/favicon.ico',
         badge: '/favicon.ico',
-      data: { url: data.url || '/' },
+        data: { url: notifUrl },
+      });
     })
   );
 });

src/fabledassistant/services/generation_task.py

@@ -358,9 +358,18 @@ async def run_generation(
         try:
             from fabledassistant.services.push import send_push_notification, vapid_enabled
             if vapid_enabled():
-                preview = buf.content_so_far[:120].rstrip()
+                text = buf.content_so_far.strip()
-                if len(buf.content_so_far) > 120:
+                if text:
+                    preview = text[:120].rstrip()
+                    if len(text) > 120:
                         preview += "…"
+                else:
+                    # Tool-only response — summarise what was done
+                    tool_names = [tc.get("function") for tc in all_tool_calls if tc.get("function")]
+                    if tool_names:
+                        preview = f"Completed: {', '.join(tool_names[:3])}"
+                    else:
+                        preview = "Action completed"
                 asyncio.create_task(send_push_notification(
                     user_id,
                     title="Response ready",
@@ -368,7 +377,7 @@ async def run_generation(
                     url=f"/chat/{conv_id}",
                 ))
         except Exception:
-            logger.debug("Failed to schedule push notification", exc_info=True)
+            logger.warning("Failed to schedule push notification", exc_info=True)
 
         # Title generation is non-critical — fire-and-forget so done fires immediately
         non_system = [m for m in messages if m["role"] != "system"]

src/fabledassistant/services/push.py

@@ -190,7 +190,7 @@ async def send_push_notification(
             )
             return response.status_code, sub.endpoint
         except Exception as e:
-            logger.warning("Push send failed for sub %d: %s", sub.id, e)
+            logger.error("Push send failed for sub %d: %s", sub.id, e, exc_info=True)
             return 0, sub.endpoint
 
     loop = asyncio.get_event_loop()
@@ -199,9 +199,12 @@ async def send_push_notification(
 
     for sub, result in zip(subscriptions, results):
         if isinstance(result, Exception):
+            logger.error("Push gather exception for user %d: %s", user_id, result, exc_info=result)
             continue
         status_code, endpoint = result
-        if status_code == 410:
+        if status_code in (200, 201):
+            logger.info("Push notification sent to sub %d (status %d)", sub.id, status_code)
+        elif status_code == 410:
             asyncio.create_task(_remove_expired_subscription(user_id, endpoint))
-        elif status_code and status_code not in (200, 201):
+        elif status_code:
-            logger.warning("Push returned status %d for user %d", status_code, user_id)
+            logger.error("Push returned unexpected status %d for user %d sub %d", status_code, user_id, sub.id)