Fix Node.js language servers failing with --user-data-dir on Windows (#50767)

Closes #50677.


Release Notes:

- Fixed Node.js language servers failing with `--user-data-dir` on
Windows

crates/paths/src/paths.rs

@@ -4,6 +4,7 @@ use std::env;
 use std::path::{Path, PathBuf};
 use std::sync::{LazyLock, OnceLock};
 
+use util::paths::SanitizedPath;
 pub use util::paths::home_dir;
 use util::rel_path::RelPath;
 
@@ -71,8 +72,14 @@ pub fn set_custom_data_dir(dir: &str) -> &'static PathBuf {
     CUSTOM_DATA_DIR.get_or_init(|| {
         let path = PathBuf::from(dir);
         std::fs::create_dir_all(&path).expect("failed to create custom data directory");
-        path.canonicalize()
-            .expect("failed to canonicalize custom data directory's path to an absolute path")
+        let canonicalized = path
+            .canonicalize()
+            .expect("failed to canonicalize custom data directory's path to an absolute path");
+        // On Windows, `canonicalize` produces extended-length paths prefixed
+        // with `\\?\`. Strip that prefix so downstream consumers (e.g.
+        // Node.js language servers) that receive derived paths as arguments
+        // don't choke on the verbatim syntax.
+        SanitizedPath::new(&canonicalized).as_path().to_path_buf()
     })
 }