Add wiki-explorer-server example (#122)

Interactive Wikipedia link graph visualization using force-graph with:
- Force-directed graph layout for exploring page connections
- Node expansion to reveal first-degree Wikipedia links
- Visual state tracking (blue=default, green=expanded, red=error)
- Direct browser access to Wikipedia pages

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

Co-authored-by: Claude <noreply@anthropic.com>

examples/wiki-explorer-server/src/global.css

@@ -0,0 +1,36 @@
+* {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+html, body {
+  font-family: system-ui, -apple-system, sans-serif;
+  font-size: 1rem;
+  width: 100%;
+  height: 100%;
+  overflow: hidden;
+}
+
+:root {
+  --bg-color: #ffffff;
+  --text-color: #333333;
+  --border-color: #dddddd;
+  --node-default: #4a90d9;
+  --node-expanded: #2ecc71;
+  --node-error: #e74c3c;
+  --link-color: rgba(128, 128, 128, 0.5);
+}
+
+@media (prefers-color-scheme: dark) {
+  :root {
+    --bg-color: #1e1e1e;
+    --text-color: #e0e0e0;
+    --border-color: #444444;
+  }
+}
+
+body {
+  background-color: var(--bg-color);
+  color: var(--text-color);
+}