Function spawn_editor_actor 

pub fn spawn_editor_actor(editor: Editor) -> EditorActorHandle

Spawn the editor actor on a dedicated thread with a current_thread tokio runtime. Takes ownership of editor.

The dedicated thread is named "lattice-editor" for observability. The actor’s tokio runtime is current_thread (single-threaded executor); editor work that needs the multi-thread LSP runtime spawns onto it via lattice_runtime::runtime::spawn_on_lsp_runtime as before (unchanged).

Returns an EditorActorHandle. Drop the handle to shut the actor down.