fix(lsp): inlay hints span issue with user config scripts (#15071)

# Description

Fixes this:

![image](https://github.com/user-attachments/assets/98b523dd-df30-4e85-b069-20aaad0d9bf5)

# User-Facing Changes

# Tests + Formatting

I can't figure out how to test this atm.
Happy to do it if someone show me some hints how.

# After Submitting

crates/nu-lsp/src/hints.rs

@@ -160,6 +160,7 @@ impl LanguageServer {
     }
 }
 
+/// TODO: test for files loaded as user config
 #[cfg(test)]
 mod tests {
     use crate::path_to_uri;

crates/nu-protocol/src/engine/engine_state.rs

@@ -880,7 +880,9 @@ impl EngineState {
         }
     }
 
-    pub fn files(&self) -> impl Iterator<Item = &CachedFile> {
+    pub fn files(
+        &self,
+    ) -> impl DoubleEndedIterator<Item = &CachedFile> + ExactSizeIterator<Item = &CachedFile> {
         self.files.iter()
     }
 

crates/nu-protocol/src/engine/state_working_set.rs

@@ -368,7 +368,15 @@ impl<'a> StateWorkingSet<'a> {
     }
 
     pub fn get_span_for_filename(&self, filename: &str) -> Option<Span> {
-        let file_id = self.files().position(|file| &*file.name == filename)?;
+        let predicate = |file: &CachedFile| &*file.name == filename;
+        // search from end to start, in case there're duplicated files with the same name
+        let file_id = self
+            .delta
+            .files
+            .iter()
+            .rposition(predicate)
+            .map(|idx| idx + self.permanent_state.num_files())
+            .or_else(|| self.permanent_state.files().rposition(predicate))?;
         let file_id = FileId::new(file_id);
 
         Some(self.get_span_for_file(file_id))