fix(core): add document content params for section edit tool (#13334)

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

## Summary by CodeRabbit

* **New Features**
* Section editing now uses the full document context to ensure edits are
consistent with the overall tone, style, and structure.
* Cleaner output for edited sections, with internal markdown comments
removed.

* **Improvements**
* Enhanced instructions and descriptions for section editing, providing
clearer guidance and examples for users.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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

@@ -1481,13 +1481,21 @@ Key requirements:
 - Maintain the original markdown formatting
 - Preserve the tone and style unless specifically asked to change it
 - Only make the requested changes
-- Return only the modified text without any explanations or comments`,
+- Return only the modified text without any explanations or comments
+- Use the full document context to ensure consistency and accuracy
+- Do not output markdown annotations like <!-- block_id=... -->`,
       },
       {
         role: 'user',
         content: `Please modify the following text according to these instructions: "{{instructions}}"
-Original text:
-{{content}}`,
+
+Full document context:
+{{document}}
+
+Section to edit:
+{{content}}
+
+Please return only the modified section, maintaining consistency with the overall document context.`,
       },
     ],
   },