Add Python REPL, instant deploy, Gist import, presentation mode, and CSS visual tools

- Python mode via Pyodide WASM runtime with stdout/stderr console integration
- Publish fiddles to clean /p/:slug URLs as standalone HTML pages
- Import code from GitHub Gist URLs with auto-detection of language/mode
- Presentation mode with slide management, fullscreen viewer, and keyboard nav
- Enable Monaco color decorators for inline CSS color pickers
- Extract reusable generateStandaloneHtml from export module

public/js/preview.js

@@ -76,6 +76,11 @@ const consoleInterceptor = `
     if (e.data && e.data.type === 'devtools-request' && e.data.tab === 'elements') sendElements();
   });
 
+  // Global helper for Pyodide stdout/stderr bridging
+  window.__fiddle_console = function(method, text) {
+    parent.postMessage({ type: 'console', method: method, args: [String(text)] }, '*');
+  };
+
   // --- Performance: timing metrics ---
   window.__fiddle_scriptStart = performance.now();
   window.addEventListener('load', function() {