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/js-preprocessors.js

@@ -89,6 +89,9 @@ export async function compileJs(code, mode) {
       return { js: code, isModule: hasModuleSyntax || hasTopLevelAwait };
     }
 
+    case 'python':
+      return compilePython(code);
+
     default:
       return { js: code };
   }
@@ -188,6 +191,34 @@ async function compileSvelte(code) {
   return { js, warnings, isModule: true };
 }
 
+function compilePython(code) {
+  // Wrap Python code in a JS loader that runs it via Pyodide in the iframe
+  const escapedCode = JSON.stringify(code);
+  const js = `
+(async function() {
+  const status = document.getElementById('pyodide-status');
+  try {
+    if (status) status.textContent = 'Loading Python runtime...';
+    const pyodide = await loadPyodide();
+    pyodide.setStdout({ batched: (text) => {
+      if (window.__fiddle_console) window.__fiddle_console('log', text);
+      else console.log(text);
+    }});
+    pyodide.setStderr({ batched: (text) => {
+      if (window.__fiddle_console) window.__fiddle_console('error', text);
+      else console.error(text);
+    }});
+    if (status) status.textContent = '';
+    await pyodide.runPythonAsync(${escapedCode});
+  } catch(e) {
+    if (status) status.textContent = '';
+    console.error('Python error: ' + e.message);
+  }
+})();
+`;
+  return { js, isModule: false };
+}
+
 /**
  * Get runtime scripts and body HTML to inject into the preview iframe.
  */
@@ -223,6 +254,12 @@ export function getFrameworkRuntime(mode) {
     case 'wasm':
       return { scripts: [], bodyHtml: '' };
 
+    case 'python':
+      return {
+        scripts: ['https://cdn.jsdelivr.net/pyodide/v0.27.2/full/pyodide.js'],
+        bodyHtml: '<div id="pyodide-status" style="font-family:monospace;color:#888;padding:12px">Loading Python...</div>',
+      };
+
     default:
       return { scripts: [], bodyHtml: '' };
   }