feat: proactive notifications — web_push channel + daily reminder check

Routes web_push through notification.py alongside NCT/email/Google Chat,
and fires daily reminder summaries via the scheduler.

- notification.py: _notify_web_push() + "web_push" case in notify();
  all four channels (web_push/email/nextcloud/google_chat) now routable
- scheduler.py: _run_reminder_check() daily at 09:00 — reads due reminders
  per persona via set_context(), formats up to 3 entries, calls notify()
- routers/settings.py: "web_push" added to valid notification_channel values
- static/settings.html: "Browser Push Notification" option in channel selector
- TODO__Agents.md: proactive notifications section marked complete

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

cortex/notification.py

@@ -114,6 +114,18 @@ async def _notify_google_chat(webhook_url: str, message: str, username: str) ->
         logger.error("notify Google Chat error for %s: %s", username, e)
 
 
+async def _notify_web_push(username: str, message: str) -> None:
+    """Send a browser push notification."""
+    import push_utils
+    result = await push_utils.send_push(username, "Cortex", message, "")
+    if "error" in result:
+        logger.warning("notify web_push error for %s: %s", username, result["error"])
+    elif result.get("sent", 0) == 0:
+        logger.debug("notify web_push: no subscriptions for %s", username)
+    else:
+        logger.info("notify web_push → %s (%d device(s))", username, result["sent"])
+
+
 async def notify(username: str, message: str, channel: str | None = None) -> None:
     """Send a notification to the user's preferred outbound channel.
 
@@ -123,6 +135,7 @@ async def notify(username: str, message: str, channel: str | None = None) -> Non
       3. "nextcloud" if notification_room is configured
       4. Silent no-op
 
+    Supported channels: "web_push", "email", "nextcloud", "google_chat"
     Configure via home/{user}/channels.json — see module docstring.
     """
     from auth_utils import get_user_channels
@@ -137,7 +150,10 @@ async def notify(username: str, message: str, channel: str | None = None) -> Non
         else:
             return
 
-    if target == "email":
+    if target == "web_push":
+        await _notify_web_push(username, message)
+
+    elif target == "email":
         email_override = channels.get("notification_email", "").strip() or None
         await _notify_email(username, message, email_override=email_override)