ui: Limit file name display length and ensure left alignment in file list

- Add MAX_DISPLAY_NAME_LEN constant (30 characters)
- Add truncate_display_name helper to truncate with ellipsis
- Apply truncation to folder names and file names
- Apply truncation to context menu file names
- Maintain left alignment through existing layout

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

src/app/file_list.rs

@@ -4,6 +4,9 @@
 
 use super::*;
 
+/// Maximum number of characters to display for a file/folder name.
+const MAX_DISPLAY_NAME_LEN: usize = 30;
+
 /// Convert a manuscript folder path to its corresponding outline file path.
 ///
 /// For the snowflake template:
@@ -40,6 +43,23 @@ fn outline_path_for_folder(folder_path: &str) -> Option<String> {
 /// Horizontal indent per folder level, in points.
 const INDENT: f32 = 12.0;
 
+/// Truncate a display name to the maximum length, adding ellipsis if needed.
+fn truncate_display_name(name: &str) -> String {
+    if name.chars().count() <= MAX_DISPLAY_NAME_LEN {
+        name.to_string()
+    } else {
+        let mut s = String::new();
+        for (i, c) in name.chars().enumerate() {
+            if i >= MAX_DISPLAY_NAME_LEN - 3 {
+                s.push_str("…");
+                break;
+            }
+            s.push(c);
+        }
+        s
+    }
+}
+
 /// One drawn line of the file tree.
 pub(super) struct Row {
     /// Workspace-relative path: the folder for a folder row, the file for a
@@ -255,7 +275,7 @@ impl App {
                                             let arrow = if open { "⏷" } else { "⏵" };
                                             let label = format!(
                                                 "{arrow} 🗀 {}",
-                                                base_name(&row.path)
+                                                truncate_display_name(base_name(&row.path))
                                             );
                                             let text = egui::RichText::new(label);
                                             let text = if in_book {
@@ -384,7 +404,8 @@ impl App {
                                                 - HANDLE_W
                                                 - reserve)
                                                 .max(24.0);
-                                            let text = egui::RichText::new(base_name(&name));
+                                            let display_name = truncate_display_name(base_name(&name));
+                                            let text = egui::RichText::new(display_name);
                                             let text = if in_book { text } else { text.weak() };
                                             let mut label = ui.add_sized(
                                                 [label_w, 20.0],
@@ -613,7 +634,7 @@ impl FileAction {
 /// The right-click menu on a file row, offering the same operations as the
 /// buttons under the list without having to select the file first.
 fn file_context_menu(ui: &mut egui::Ui, name: &str, idx: usize, action: &mut Option<FileAction>) {
-    ui.label(egui::RichText::new(base_name(name)).strong());
+    ui.label(egui::RichText::new(truncate_display_name(base_name(name))).strong());
     ui.separator();
     let mut pick = |ui: &mut egui::Ui, label: &str, hover: &str, chosen: FileAction| {
         if ui.button(label).on_hover_text(hover).clicked() {