Completion always times out

首先，在大型 Xcode workspace 中复现 completion，并检查提供的 logs，尤其是 extractPrompt timeout 和 related-files 处理。完成的标准是，completion requests 在大型 workspaces 中不再超时，同时继续在 standalone files 中正常工作。

Describe the bug
When working in a relatively large xcode workspace, the completion seems to pretty much not work at all, and whenever I check the logs I see that the completion request seems to time out every time, it works instantly in some of the projects though.

If I open the same file by itself the completions work again.

Versions

• Copilot for Xcode: 0.40.0
• Xcode: 16.4
• macOS: 15.5

Steps to reproduce

1. Open a large xcode workspace
2. Type in a file or trigger completion using the get completion button/shortcut
3. Nothing happens

Logs

[2025-08-12T07:55:26.491Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "message" : "[getCompletions] Requesting for file: ---redacted--- at 37:14 between \"\\n    var descri\" and \"\\n}\\n\".",
  "type" : 4
}
[2025-08-12T07:55:26.491Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "type" : 4,
  "message" : "[relatedFiles] Fetching related files for file: ---redacted---"
}
[2025-08-12T07:55:26.491Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "message" : "[relatedFiles] `copilot\/related` not supported",
  "type" : 4
}
[2025-08-12T07:55:26.491Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "message" : "[relatedFiles] Fetched 0 related files for 'file: ---redacted---' in 0.10320900002261624ms.",
  "type" : 4
}
[2025-08-12T07:55:26.491Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "message" : "[relatedFiles] Fetched following traits  for 'file:---redacted---",
  "type" : 4
}
[2025-08-12T07:55:27.690Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "message" : "[ghostText] Timeout during extractPrompt",
  "type" : 4
}
[2025-08-12T07:55:27.690Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "message" : "[getCompletions] No ghostText produced -- abortedBeforeIssued: Timeout",
  "type" : 4
}
[2025-08-12T07:55:27.941Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "type" : 4,
  "message" : "[relatedFiles] Fetched following traits  for 'file:---redacted---'"
}
[2025-08-12T07:55:27.941Z] [info] [GitHubCopilot] [31488] window/logMessage: {
  "type" : 4,
  "message" : "[relatedFiles] neighborFiles.getNeighborFilesAndTraits 0 related files found for file:---redacted---"
}