Fix game URLs - remove .md extension from links

URLs now work correctly:
- Homepage links to games without .md extension
- Individual game pages accessible at clean URLs
- Example: /games/quantum-game-with-photons instead of /games/quantum-game-with-photons.md

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

Co-Authored-By: Claude <[email protected]>

Author: stared

site/src/pages/games/[...id].astro

@@ -5,7 +5,7 @@ import Layout from '../../layouts/Layout.astro';
 export async function getStaticPaths() {
   const games = await getCollection('games');
   return games.map(game => ({
-    params: { id: game.id },
+    params: { id: game.id.replace('.md', '') },
     props: { game },
   }));
 }

site/src/pages/index.astro

@@ -70,7 +70,7 @@ const gamesByCategory = categories.reduce((acc, category) => {
           <div class="grid gap-4 md:grid-cols-2 lg:grid-cols-3">
             {gamesByCategory[category].map(game => (
               <a
-                href={`/games/${game.id}`}
+                href={`/games/${game.id.replace('.md', '')}`}
                 class="game-card block p-4 border border-gray-200 rounded hover:border-gray-400 transition-colors space-y-2"
                 data-title={game.data.title.toLowerCase()}
                 data-topics={game.data.topics.join(',').toLowerCase()}