Reuse existing language servers for invisible worktrees (#30707)

Closes https://github.com/zed-industries/zed/issues/20767

Before:


https://github.com/user-attachments/assets/6438eb26-796a-4586-9b20-f49d9a133624


After:



https://github.com/user-attachments/assets/b3fc2f8b-2873-443f-8d80-ab4a35cf0c09



Release Notes:

- Fixed external files spawning extra language servers

crates/project/src/manifest_tree.rs

@@ -27,7 +27,9 @@ use crate::{
     worktree_store::{WorktreeStore, WorktreeStoreEvent},
 };
 
-pub(crate) use server_tree::{AdapterQuery, LanguageServerTree, LaunchDisposition};
+pub(crate) use server_tree::{
+    AdapterQuery, LanguageServerTree, LanguageServerTreeNode, LaunchDisposition,
+};
 
 struct WorktreeRoots {
     roots: RootPathTrie<ManifestName>,