fix: 修复 SVG 图片导致 tesseract.js 崩溃的问题 (#69)

SVG 是基于 XML 的矢量图格式，tesseract.js 无法处理。
尝试对 SVG 进行 OCR 会在 tesseract Worker 内部通过 process.nextTick
抛出未捕获的 TypeError (fetch failed)，导致整个进程异常终止。

修复方案：在三层防御点过滤 SVG 图片：
1. converter.ts preprocessImages(): 下载/读取后检测 content-type
   或文件扩展名为 SVG 时，替换为文本描述
2. vision.ts applyVisionInterceptor(): 在分发到 OCR/Vision API
   之前过滤 SVG 类型的 image block
3. vision.ts processWithLocalOCR(): 在调用 worker.recognize()
   之前检查 UNSUPPORTED_OCR_TYPES 集合（纵深防御）

src/converter.ts

@@ -1196,8 +1196,18 @@ async function preprocessImages(messages: AnthropicMessage[]): Promise<void> {
                             if (!existsSync(resolvedPath)) {
                                 throw new Error(`File not found: ${resolvedPath}`);
                             }
-                            const fileBuffer = readFileSync(resolvedPath);
                             const mediaType = guessMediaType(resolvedPath);
+                            // ★ SVG 是矢量图格式（XML），无法被 OCR 或 Vision API 处理
+                            //   tesseract.js 处理 SVG 会抛出 unhandled error 导致进程崩溃
+                            if (mediaType === 'image/svg+xml') {
+                                console.log(`[Converter] ⚠️ 跳过 SVG 矢量图（不支持 OCR/Vision）: ${resolvedPath}`);
+                                msg.content[i] = {
+                                    type: 'text',
+                                    text: `[SVG vector image attached: ${resolvedPath.substring(resolvedPath.lastIndexOf('/') + 1)}. SVG images are XML-based vector graphics and cannot be processed by OCR/Vision. The image likely contains a logo, icon, badge, or diagram.]`,
+                                } as any;
+                                continue;
+                            }
+                            const fileBuffer = readFileSync(resolvedPath);
                             const base64Data = fileBuffer.toString('base64');
                             msg.content[i] = {
                                 ...block,
@@ -1228,6 +1238,16 @@ async function preprocessImages(messages: AnthropicMessage[]): Promise<void> {
                             const buffer = Buffer.from(await response.arrayBuffer());
                             const contentType = response.headers.get('content-type') || 'image/jpeg';
                             const mediaType = contentType.split(';')[0].trim();
+                            // ★ SVG 是矢量图格式（XML），无法被 OCR 或 Vision API 处理
+                            //   tesseract.js 处理 SVG 会抛出 unhandled error 导致进程崩溃（#69）
+                            if (mediaType === 'image/svg+xml' || imageUrl.toLowerCase().endsWith('.svg')) {
+                                console.log(`[Converter] ⚠️ 跳过 SVG 矢量图（不支持 OCR/Vision）: ${imageUrl.substring(0, 100)}`);
+                                msg.content[i] = {
+                                    type: 'text',
+                                    text: `[SVG vector image from URL: ${imageUrl}. SVG images are XML-based vector graphics and cannot be processed by OCR/Vision. The image likely contains a logo, icon, badge, or diagram.]`,
+                                } as any;
+                                continue;
+                            }
                             const base64Data = buffer.toString('base64');
                             // 替换为 base64 格式
                             msg.content[i] = {

src/vision.ts

@@ -26,6 +26,16 @@ export async function applyVisionInterceptor(messages: AnthropicMessage[]): Prom
 
     for (const block of lastUserMsg.content) {
         if (block.type === 'image') {
+            // ★ 跳过 SVG 矢量图 — tesseract.js 无法处理 SVG，会导致进程崩溃 (#69)
+            const mediaType = (block as any).source?.media_type || '';
+            if (mediaType === 'image/svg+xml') {
+                console.log('[Vision] ⚠️ 跳过 SVG 矢量图（不支持 OCR/Vision 处理）');
+                newContent.push({
+                    type: 'text',
+                    text: '[SVG vector image was attached but cannot be processed by OCR/Vision. It likely contains a logo, icon, badge, or diagram.]',
+                });
+                continue;
+            }
             hasImages = true;
             imagesToAnalyze.push(block);
         } else {
@@ -60,6 +70,9 @@ export async function applyVisionInterceptor(messages: AnthropicMessage[]): Prom
     }
 }
 
+// ★ 不支持 OCR 的图片格式（矢量图、动画等）
+const UNSUPPORTED_OCR_TYPES = new Set(['image/svg+xml']);
+
 async function processWithLocalOCR(imageBlocks: AnthropicContentBlock[]): Promise<string> {
     const worker = await createWorker('eng+chi_sim');
     let combinedText = '';
@@ -69,6 +82,11 @@ async function processWithLocalOCR(imageBlocks: AnthropicContentBlock[]): Promis
         let imageSource: string | Buffer = '';
 
         if (img.type === 'image' && img.source) {
+            // ★ 防御性检查：跳过不支持 OCR 的格式（#69 - SVG 导致 tesseract 崩溃）
+            if (UNSUPPORTED_OCR_TYPES.has(img.source.media_type || '')) {
+                combinedText += `--- Image ${i + 1} ---\n(Skipped: ${img.source.media_type} format is not supported by OCR)\n\n`;
+                continue;
+            }
             const sourceData = img.source.data || img.source.url;
             if (img.source.type === 'base64' && sourceData) {
                 const mime = img.source.media_type || 'image/jpeg';