🩹 Use workspace root when running just-lsp

[nefrob]

Description:

Re #90.

• Set workspace root as the current working directory when spawning the LSP binary. This allows version managers (mise, asdf, rtx, etc.) to properly resolve tool versions based on project configuration files.

Testing/Screenshots:

• Validated update works with mise install /Users/robertneff/.local/share/mise/installs/cargo-just-lsp/0.3.4/bin/just-lsp