Support relative paths in LSP & DAP binaries (#42135)

Closes #41214

Release Notes:

- Added support for relative paths in LSP and DAP binaries

---------

Co-authored-by: Cole Miller <cole@zed.dev>
Co-authored-by: Julia Ryan <juliaryan3.14@gmail.com>

crates/worktree/src/worktree.rs

@@ -2352,8 +2352,8 @@ impl Snapshot {
         self.entries_by_path.first()
     }
 
-    /// TODO: what's the difference between `root_dir` and `abs_path`?
-    /// is there any? if so, document it.
+    /// Returns `None` for a single file worktree, or `Some(self.abs_path())` if
+    /// it is a directory.
     pub fn root_dir(&self) -> Option<Arc<Path>> {
         self.root_entry()
             .filter(|entry| entry.is_dir())