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/mcp-app.html

@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+  <meta charset="UTF-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1.0">
+  <title>Wiki Explorer</title>
+</head>
+<body>
+  <div id="graph"></div>
+  <div id="popup">
+    <div class="popup-title"></div>
+    <div class="popup-error"></div>
+    <div class="popup-buttons">
+      <button id="open-btn">Open</button>
+      <button id="expand-btn">Expand</button>
+    </div>
+  </div>
+  <div id="controls">
+    <button id="reset-graph" title="Reset graph">&#x21BA;</button>
+    <div id="zoom-controls">
+      <button id="zoom-in" title="Zoom in">+</button>
+      <button id="zoom-out" title="Zoom out">−</button>
+    </div>
+  </div>
+  <script type="module" src="/src/mcp-app.ts"></script>
+</body>
+</html>