feat(core): add section edit tool (#13313)

Close [AI-396](https://linear.app/affine-design/issue/AI-396)

<img width="798" height="294" alt="截屏2025-07-25 11 30 32"
src="https://github.com/user-attachments/assets/6366dab2-688b-470b-8b24-29a2d50a38c9"
/>



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

## Summary by CodeRabbit

* **New Features**
* Introduced a "Section Edit" AI tool for expert editing of specific
markdown sections based on user instructions, preserving formatting and
style.
* Added a new interface and UI component for section editing, allowing
users to view, copy, insert, or save edited content directly from chat
interactions.

* **Improvements**
* Enhanced AI chat and tool rendering to support and display section
editing results.
* Updated chat input handling for improved draft management and message
sending order.

* **Other Changes**
* Registered the new section editing tool in the system for seamless
integration.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/plugins/copilot/providers/provider.ts

@@ -29,6 +29,7 @@ import {
   createDocSemanticSearchTool,
   createExaCrawlTool,
   createExaSearchTool,
+  createSectionEditTool,
 } from '../tools';
 import { CopilotProviderFactory } from './factory';
 import {
@@ -224,6 +225,10 @@ export abstract class CopilotProvider<C = any> {
             tools.doc_compose = createDocComposeTool(prompt, this.factory);
             break;
           }
+          case 'sectionEdit': {
+            tools.section_edit = createSectionEditTool(prompt, this.factory);
+            break;
+          }
         }
       }
       return tools;

packages/backend/server/src/plugins/copilot/providers/types.ts

@@ -73,6 +73,8 @@ export const PromptConfigStrictSchema = z.object({
       'webSearch',
       // artifact tools
       'docCompose',
+      // section editing
+      'sectionEdit',
     ])
     .array()
     .nullable()