fix: Change file list panel from show_animated to show

show_animated may have issues with width persistence when resizing.
Using show() instead should allow the panel to remember its width.

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>

src/app/file_list.rs

@@ -171,7 +171,7 @@ impl App {
             // that asks for more width than there is would otherwise push it
             // wider every frame.
             .width_range(160.0..=460.0)
-            .show_animated(ctx, show_files, |ui| {
+            .show(ctx, show_files, |ui| {
                 // The default theme renders unselected list rows fairly dim; bump
                 // the widget text colours so file names stay legible (especially in
                 // dark mode) without affecting the rest of the app.