feat: add ai writing imitation mode

frontend-web/src/open-canvas/api/ai-writing-sample.ts

@@ -0,0 +1,23 @@
+import { getBackendBaseURL } from '@/core/config';
+import { apiFetch } from '@/core/api';
+
+export interface AIWritingSampleExtractResult {
+  filename: string;
+  text: string;
+  char_count: number;
+  truncated: boolean;
+}
+
+export async function extractAIWritingSample(file: File): Promise<AIWritingSampleExtractResult> {
+  const form = new FormData();
+  form.append('file', file);
+  const resp = await apiFetch(`${getBackendBaseURL()}/api/ai-writing/sample/extract`, {
+    method: 'POST',
+    body: form,
+  });
+  if (!resp.ok) {
+    const text = await resp.text().catch(() => '');
+    throw new Error(text || `样文解析失败：${resp.status}`);
+  }
+  return resp.json();
+}