Default root_uri to the workspace

[acottis]

On windows using JDT Language server the LSP would crash on opening a .java file in which it would not resolve a root path when calling find_lsp_workspace.

This is because the JDT language server does not accept non URI paths on windows for example C:\foo\bar which is being passed by the root_path variable.

If we always set root_uri when possible it will use that and get the correctly formatted file:// URI.

To reproduce this issue on windows you just need to make create a java file anywhere it will not find the lsp workspace, for example hx C:\tmp\main.java then look at the log and see the below:

2025-11-07T21:27:19.374 helix_lsp::transport [ERROR] jdtls err <- "Caused by: java.net.URISyntaxException: Illegal character in opaque part at index 2: C:\\tmp\r\n"

I am not very familiar with the codebase so not sure of why we cant do this, just wanted to make a PR as it resolved my issue. Not sure about the implications on other OS's language servers.