Initial commit — AI-powered coding tutor (Professor)

Next.js 16, React 19, Monaco editor, Anthropic SDK, multi-provider AI,
Wandbox Python execution, iframe HTML preview, SQLite auth + session persistence.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hooks/useCodeExecution.ts

@@ -0,0 +1,51 @@
+import type { Dispatch } from 'react';
+import type { AppAction, SupportedLanguage } from '@/types';
+
+const MAX_CODE_LENGTH = 10_000;
+
+export function useCodeExecution(dispatch: Dispatch<AppAction>) {
+  async function execute(language: SupportedLanguage, code: string): Promise<void> {
+    if (code.trim().length === 0) return;
+
+    if (code.length > MAX_CODE_LENGTH) {
+      dispatch({ type: 'SET_ERROR', payload: 'Code exceeds the 10,000 character limit.' });
+      return;
+    }
+
+    // HTML is handled by HtmlPreview client-side
+    if (language === 'html') {
+      return;
+    }
+
+    dispatch({ type: 'EXECUTE_START' });
+
+    try {
+      const res = await fetch('/api/execute', {
+        method: 'POST',
+        headers: { 'Content-Type': 'application/json' },
+        body: JSON.stringify({ language, code }),
+      });
+
+      if (!res.ok) {
+        const data = await res.json().catch(() => ({}));
+        throw new Error(data.error ?? `Server error ${res.status}`);
+      }
+
+      const result = await res.json();
+      dispatch({ type: 'EXECUTE_DONE', payload: result });
+    } catch (err) {
+      dispatch({
+        type: 'EXECUTE_DONE',
+        payload: {
+          stdout: '',
+          stderr: '',
+          exitCode: -1,
+          timedOut: false,
+          error: err instanceof Error ? err.message : 'Execution failed',
+        },
+      });
+    }
+  }
+
+  return { execute };
+}