Add system-monitor-server example

Demo MCP App showcasing real-time OS metrics visualization with:
- Per-core CPU usage via stacked area chart (Chart.js)
- Memory usage bar gauge with color-coded thresholds
- Auto-polling at 2-second intervals
- Light/dark theme support

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

examples/system-monitor-server/src/global.css

@@ -0,0 +1,12 @@
+* {
+  box-sizing: border-box;
+}
+
+html, body {
+  font-family: system-ui, -apple-system, sans-serif;
+  font-size: 1rem;
+}
+
+code {
+  font-size: 1em;
+}