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>

index.html

@@ -217,7 +217,7 @@
 			const emoteEl = document.getElementById("emote");
 			const messageEl = document.getElementById("message");
 			const POLL_INTERVAL = 2000;
-			const VERSION = "v1.4.0";
+			const VERSION = "v1.5.0";
 
 			// Sound system
 			let audioCtx = null;