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>

openapi.yaml

@@ -14,7 +14,7 @@ info:
     ## TTL/Heartbeat Pattern
     Events can have a TTL (time-to-live) that auto-expires them. Detectors typically send
     heartbeat events that expire if not refreshed, indicating loss of communication.
-  version: 1.4.0
+  version: 1.5.0
   license:
     name: MIT