Return correct source type for pyi files

crates/ruff_server/src/session/index.rs

@@ -1,9 +1,7 @@
 use anyhow::anyhow;
 use rustc_hash::FxHashMap;
 use std::{
-    collections::BTreeMap,
-    path::{Path, PathBuf},
-    sync::Arc,
+    collections::BTreeMap, path::{Path, PathBuf}, sync::Arc
 };
 
 use crate::{
@@ -465,7 +463,7 @@ impl DocumentQuery {
     /// Get the source type of the document associated with this query.
     pub(crate) fn source_type(&self) -> ruff_python_ast::PySourceType {
         match self {
-            Self::Text { .. } => ruff_python_ast::PySourceType::Python,
+            Self::Text { .. } => ruff_python_ast::PySourceType::from(self.file_path()),
             Self::Notebook { .. } => ruff_python_ast::PySourceType::Ipynb,
         }
     }