当触发定时的lua诊断时, 无法操作代码块的折叠或展开

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### How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

### Which OS are you using?

Windows

### What is the issue affecting?

Diagnostics/Syntax Checking

### Expected Behaviour

折叠功能应该在插件的诊断阶段和非诊断阶段都是正常的

### Actual Behaviour

当触发定时的lua诊断时, 折叠的代码块会有以下可能:
1. 折叠自动展开
2. 无法折叠或者展开

### Reproduction steps

1. Go to
2. Click
3. See error

### Additional Notes

_No response_

### Log File

_No response_

Reproduce the issue on Windows in the Visual Studio Code Extension while scheduled Lua diagnostics run, comparing folding before, during, and after diagnostics. No source file, test, or log is identified, so trace the interaction between diagnostics and folding; done means code blocks remain foldable and expandable in every state.

Written by the indexing model from the issue text.