Guidance on pattern to improve context for completions in an IDE

## Background

Our IDE has an opt-in feature where it will tell copilot about all files in the current project by doing `textDocument/didOpen` on them. This could potentially be dozens, possibly even hundreds of files, given the nature of the projects in real-world use.

This was originally implemented using the vim copilot plugin, now switched to using `copilot-language-server`.

## Question

Is this a "Good Idea"? Will it actually improve completion suggestions by providing more context, or will it quickly hit some internal limit?

When I switched this to `copilot-language-server` I also implemented setting `workspaceFolders` to true, and pass the root folder of the project as the workspace folder; is that accomplishing anything in terms of improving awareness of other files in the project (i.e. does this make the "pretend to open all files" approach redundant)?

Thanks!

审查 vim copilot plugin 的行为、切换到 copilot-language-server 的过程，以及 issue 中描述的 workspaceFolders 和 textDocument/didOpen 处理方式。确定打开项目中的每个文件是否能改善补全上下文，还是会达到限制，然后记录推荐的模式，以及 workspaceFolders 是否会使这种方法变得多余。

由索引模型根据 Issue 内容生成。