Bump to v1.5.0: deduplicate detectors, fix aggregator bugs, fix blocking I/O

- Extract shared send_event/clear_event into detectors/base.py, removing
  ~150 lines of duplication across all 6 detectors
- Fix default aggregator URL from port 5000 to 5100 in all detectors
- Standardize cpu.py and memory.py to use active_alerts set pattern
- Fix immediate emote rotation on startup (last_emote_change = time.time())
- Extract magic numbers to named constants in aggregator
- Protect write_status() with try/except OSError
- Fix notify event ID collision with monotonic counter
- Replace blocking stream_output() with background daemon threads in kao.py

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

detectors/base.py

@@ -0,0 +1,35 @@
+"""
+Shared utilities for Kao detectors.
+"""
+
+import requests
+
+DEFAULT_AGGREGATOR_URL = "http://localhost:5100"
+
+
+def send_event(url, event_id, priority, message, check_interval):
+    """Send an event to the aggregator with heartbeat TTL."""
+    ttl = check_interval * 2
+    try:
+        response = requests.post(
+            f"{url}/event",
+            json={"id": event_id, "priority": priority, "message": message, "ttl": ttl},
+            timeout=5,
+        )
+        print(f"[EVENT] {event_id}: {message} (priority {priority}, ttl {ttl}s) -> {response.status_code}")
+    except requests.RequestException as e:
+        print(f"[ERROR] Failed to send event: {e}")
+
+
+def clear_event(url, event_id):
+    """Clear an event from the aggregator."""
+    try:
+        response = requests.post(
+            f"{url}/clear",
+            json={"id": event_id},
+            timeout=5,
+        )
+        if response.status_code == 200:
+            print(f"[CLEAR] {event_id}")
+    except requests.RequestException as e:
+        print(f"[ERROR] Failed to clear event: {e}")