Pre-launch fixes: error handling, cleanup, consistency

- Remove unused claude-agent-sdk from host deps (only used in container)
- Remove dead scheduler MCP config (built into IPC)
- Remove unused eslint script
- Add clear error message when Apple Container fails to start
- Auto-generate launchd plist with real paths in setup skill
- Standardize Node.js version to 20+ everywhere

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.mcp.json

@@ -3,10 +3,6 @@
     "gmail": {
       "command": "npx",
       "args": ["-y", "@gongrzhe/server-gmail-autoauth-mcp"]
-    },
-    "scheduler": {
-      "command": "npx",
-      "args": ["-y", "schedule-task-mcp"]
     }
   }
 }