fix: PDF attachments sent as document blocks instead of image blocks

PDF files were incorrectly wrapped as type:'image' content blocks,
causing Claude API to reject them as "Invalid image data".

- conversation-context.service: check mediaType for application/pdf,
  use type:'document' block (Anthropic native PDF support) instead
- claude-agent-sdk-engine: detect both 'image' and 'document' blocks
  when deciding to build multimodal SDK prompt

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

packages/services/agent-service/src/domain/services/conversation-context.service.ts

@@ -87,17 +87,30 @@ export class ConversationContextService {
     for (const msg of messages) {
       if (msg.role === 'user') {
         if (msg.attachments && msg.attachments.length > 0) {
-          // Build multimodal content blocks for messages with images
+          // Build multimodal content blocks for messages with attachments
           const contentBlocks: any[] = [];
           for (const att of msg.attachments) {
-            contentBlocks.push({
-              type: 'image',
-              source: {
-                type: 'base64',
-                media_type: att.mediaType,
-                data: att.base64Data,
-              },
-            });
+            if (att.mediaType === 'application/pdf') {
+              // PDF → Anthropic document content block
+              contentBlocks.push({
+                type: 'document',
+                source: {
+                  type: 'base64',
+                  media_type: 'application/pdf',
+                  data: att.base64Data,
+                },
+              });
+            } else {
+              // Image → Anthropic image content block
+              contentBlocks.push({
+                type: 'image',
+                source: {
+                  type: 'base64',
+                  media_type: att.mediaType,
+                  data: att.base64Data,
+                },
+              });
+            }
           }
           if (msg.content && msg.content !== '[图片]') {
             contentBlocks.push({ type: 'text', text: msg.content });

packages/services/agent-service/src/infrastructure/engines/claude-agent-sdk/claude-agent-sdk-engine.ts

@@ -470,19 +470,21 @@ export class ClaudeAgentSdkEngine implements AgentEnginePort {
       return params.prompt;
     }
 
-    // Check if the last message in history is a user message with image content blocks
+    // Check if the last message in history is a user message with multimodal content blocks
     const lastMsg = history[history.length - 1];
-    const hasImageBlocks =
+    const hasMultimodalBlocks =
       lastMsg.role === 'user' &&
       Array.isArray(lastMsg.content) &&
-      lastMsg.content.some((block: any) => block.type === 'image');
+      lastMsg.content.some(
+        (block: any) => block.type === 'image' || block.type === 'document',
+      );
 
-    if (!hasImageBlocks) {
+    if (!hasMultimodalBlocks) {
       return params.prompt;
     }
 
-    // Build a single SDKUserMessage with multimodal content
-    this.logger.log(`Building multimodal SDK prompt with image content blocks`);
+    // Build a single SDKUserMessage with multimodal content (images + documents)
+    this.logger.log(`Building multimodal SDK prompt with content blocks`);
 
     const userMessage = {
       type: 'user' as const,