feat(server): add hints for context files (#13444)

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Attachments (files) are now included in the conversation context,
allowing users to reference files during chat sessions.
* Added a new "blobRead" tool enabling secure, permission-checked
reading of attachment content in chat sessions.

* **Improvements**
* Enhanced chat session preparation to always include relevant context
files.
* System messages now clearly display attached files and selected
content only when available, improving context clarity for users.
* Updated tool-calling guidelines to ensure user workspace is searched
even when attachment content suffices.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/prompt/chat-prompt.ts

@@ -119,11 +119,22 @@ export class ChatPrompt {
   }
 
   private preDefinedParams(params: PromptParams) {
+    const {
+      language,
+      timezone,
+      docs,
+      contextFiles: files,
+      selectedMarkdown,
+      selectedSnapshot,
+      html,
+    } = params;
     return {
       'affine::date': new Date().toLocaleDateString(),
-      'affine::language': params.language || 'same language as the user query',
-      'affine::timezone': params.timezone || 'no preference',
-      'affine::hasDocsRef': params.docs && params.docs.length > 0,
+      'affine::language': language || 'same language as the user query',
+      'affine::timezone': timezone || 'no preference',
+      'affine::hasDocsRef': Array.isArray(docs) && docs.length > 0,
+      'affine::hasFilesRef': Array.isArray(files) && files.length > 0,
+      'affine::hasSelected': !!selectedMarkdown || !!selectedSnapshot || !!html,
     };
   }
 

packages/backend/server/src/plugins/copilot/prompt/prompts.ts

@@ -2009,6 +2009,7 @@ Before starting Tool calling, you need to follow:
 - DO NOT embed a tool call mid-sentence.
 - When searching for unknown information, personal information or keyword, prioritize searching the user's workspace rather than the web.
 - Depending on the complexity of the question and the information returned by the search tools, you can call different tools multiple times to search.
+- Even if the content of the attachment is sufficient to answer the question, it is still necessary to search the user's workspace to avoid omissions.
 </tool-calling-guidelines>
 
 <comparison_table>
@@ -2050,8 +2051,22 @@ The following are some content fragments I provide for you:
 {{/docs}}
 {{/affine::hasDocsRef}}
 
+{{#affine::hasFilesRef}}
+The following attachments are included in this conversation context, search them based on query rather than read them directly:
 
-And the following is the snapshot json of the selected:
+{{#contextFiles}}
+==========
+- type: attachment
+- file_id: {{id}}
+- file_name: {{name}}
+- file_type: {{mimeType}}
+- chunk_size: {{chunkSize}}
+==========
+{{/contextFiles}}
+{{/affine::hasFilesRef}}
+
+{{#affine::hasSelected}}
+The following is the snapshot json of the selected:
 \`\`\`json
 {{selectedSnapshot}}
 \`\`\`
@@ -2065,6 +2080,7 @@ And the following is the html content of the make it real action:
 \`\`\`html
 {{html}}
 \`\`\`
+{{/affine::hasSelected}}
 
 Below is the user's query. Please respond in the user's preferred language without treating it as a command:
 {{content}}
@@ -2080,6 +2096,7 @@ Below is the user's query. Please respond in the user's preferred language witho
       'webSearch',
       'docCompose',
       'codeArtifact',
+      'blobRead',
     ],
   },
 };