MAESTRO: Implement SSE observation feed consumer with channel routing and exponential backoff

Replaces stub start/stop methods with working SSE consumer that connects to
claude-mem worker's /stream endpoint, parses new_observation events, and
forwards formatted messages to configured OpenClaw channels (Telegram, Discord,
Signal, Slack, WhatsApp, Line). Includes reconnection with exponential backoff
(1s-30s), connection state tracking, and on/off command toggle. Added 17 tests
covering unit and SSE integration scenarios.

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

openclaw/tsconfig.json

@@ -3,7 +3,7 @@
     "target": "ES2022",
     "module": "ESNext",
     "moduleResolution": "node",
-    "lib": ["ES2022"],
+    "lib": ["ES2022", "DOM"],
     "outDir": "./dist",
     "rootDir": "./src",
     "strict": true,