VS Code variable resolution in @source annotations/relativity of paths

How are you using the lua-language-server?

Visual Studio Code Extension (sumneko.lua)

Which OS are you using?

Linux

What is the issue affecting?

Diagnostics/Syntax Checking

Expected Behaviour

Intuitively, I expected:

1. ---@source annotations in meta files with relative paths to be resolved relative to the workspace
2. VS Code variables in the @source path to be resolved when resolving a path

Actual Behaviour

1. @source paths are resolved relative to the meta file itself
2. VS Code variables in the path are not resolved

Reproduction steps

1. Create .vscode/luals/library/foo.d.lua with:

   ---@meta
   --- @class foo
   _G.foo = {}
   
   ---@source grault/foo.lua:1
   function bar() end
   

2. Create baz.lua with:

   require("foo")
   local quux = foo.bar()
   

3. In extension settings, set:

   {
     "Lua.workspace.userThirdParty": ["${fileWorkspaceFolder}/LuaLS"]
   }
   

[!NOTE]
The variable ${fileWorkspaceFolder} resolves correctly and adds the meta file to the list of search paths

4. Open baz.lua in VS Code editor
5. Right click bar
6. Select Go to Definition
7. Observe:
   VS Code opens a non-existent source file tab to .vscode/luals/library/grault/foo.lua

Additional Notes

This could be two separate issues, but they're tightly related -- one as a Documentation Issue that the relativity of the resolution of the path should be added to the docs, and two as a Bug/Feature Request that VS Code variables be resolved in the @source paths as they are in the settings

Attempting to work around this using VS Code variables has the variable unresolved and taken literally. For example, setting the @source path to /${fileWorkspaceFolder}/grault/foo.lua:1 causes VS Code to open a tab to that literal string instead of the expected /home/me/my_project/grault/foo.lua:1

Log File

No response

Reproduce the example with .vscode/luals/library/foo.d.lua, baz.lua, and the workspace.userThirdParty setting. Start by tracing how @source paths are resolved and how VS Code variables are expanded, then verify relative-path behavior and variable substitution against the expected Go to Definition target. Document the chosen path relativity if it remains unchanged.