Add outline popup window for folder context menu

Implement the outline file popup window that opens when a user
right-clicks on a folder in the file list (e.g., Act 1 in 06-First Draft)
and selects 'Outline' from the context menu. The window displays the
corresponding outline file (e.g., 04-Outline/scene_breakdown/act_01.md)
in a read-only view.

Changes:
- Add outline_popup_window() function in file_list.rs
- Add window rendering call in mod.rs update loop
- Popup reads file content on open and displays it in scrollable view

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

src/app/file_list.rs

@@ -4,6 +4,39 @@
 
 use super::*;
 
+/// Convert a manuscript folder path to its corresponding outline file path.
+///
+/// For the snowflake template:
+/// - `06-First Draft/Act 1` → `04-Outline/scene_breakdown/act_01.md`
+/// - `06-First Draft/Act 2` → `04-Outline/scene_breakdown/act_02.md`
+/// - etc.
+fn outline_path_for_folder(folder_path: &str) -> Option<String> {
+    // Split the path into components
+    let parts: Vec<&str> = folder_path.split('/').collect();
+    
+    // We expect paths like "06-First Draft/Act 1"
+    if parts.len() < 2 {
+        return None;
+    }
+    
+    let last_part = parts.last()?;
+    let folder_name = last_part.trim();
+    
+    // Try to extract the act number from the folder name
+    // "Act 1", "Act 2", "Act 3" etc.
+    let act_num = if folder_name.starts_with("Act ") {
+        folder_name.trim_start_matches("Act ").trim().parse::<u32>().ok()
+    } else {
+        None
+    };
+    
+    act_num.map(|n| {
+        // Format as act_01, act_02, etc.
+        let act_str = if n < 10 { format!("act_0{}", n) } else { format!("act_{}", n) };
+        format!("04-Outline/scene_breakdown/{}.md", act_str)
+    })
+}
+
 /// Horizontal indent per folder level, in points.
 const INDENT: f32 = 12.0;
 
@@ -175,6 +208,7 @@ impl App {
                 // What the right-click menu picked, applied further down: the
                 // row closure below is still borrowing `self` to draw with.
                 let mut action: Option<FileAction> = None;
+                let mut outline_action: Option<String> = None;
                 let pointer = ui.input(|i| i.pointer.interact_pos());
                 // Filtering happens on the flat list, so folders left with no
                 // files simply stop appearing.
@@ -237,18 +271,28 @@ impl App {
                                             // widened. The full path is on hover.
                                             let name_w =
                                                 (row_width - indent - COUNT_W).max(48.0);
-                                            if ui
+                                            let button_response = ui
                                                 .add_sized(
                                                     [name_w, 20.0],
                                                     egui::Button::new(text)
                                                         .frame(false)
                                                         .truncate(),
                                                 )
-                                                .on_hover_text(&row.path)
-                                                .clicked()
-                                            {
+                                                .on_hover_text(&row.path);
+                                            
+                                            if button_response.clicked() {
                                                 toggled = Some(row.path.clone());
                                             }
+                                            
+                                            // Add context menu for folders that have corresponding outline files
+                                            if let Some(outline_path) = outline_path_for_folder(&row.path) {
+                                                button_response.context_menu(|ui| {
+                                                    if ui.button("Outline").clicked() {
+                                                        outline_action = Some(outline_path);
+                                                        ui.close_menu();
+                                                    }
+                                                });
+                                            }
                                             ui.label(
                                                 egui::RichText::new(count.to_string())
                                                     .small()
@@ -455,6 +499,10 @@ impl App {
                     let ctx = ui.ctx().clone();
                     self.apply_file_action(action, &ctx);
                 }
+                if let Some(outline_path) = outline_action {
+                    // Open the outline file
+                    self.open_outline_file = Some(outline_path);
+                }
 
                 ui.separator();
                 ui.horizontal(|ui| {
@@ -879,3 +927,49 @@ mod tests {
         assert!(sketch(&[], &[]).is_empty());
     }
 }
+
+impl App {
+    /// The outline file popup window: displays the content of an outline file
+    /// opened from a folder context menu.
+    pub(super) fn outline_popup_window(&mut self, ctx: &egui::Context) {
+        let outline_path = match self.open_outline_file.clone() {
+            Some(p) => p,
+            None => return,
+        };
+        
+        let abs_path = self.path_for(&outline_path);
+        let content = match std::fs::read_to_string(&abs_path) {
+            Ok(content) => content,
+            Err(e) => {
+                self.status = format!("Could not read {}: {}", outline_path, e);
+                self.open_outline_file = None;
+                return;
+            }
+        };
+        
+        let mut open = true;
+        
+        egui::Window::new(format!("Outline — {}", outline_path))
+            .open(&mut open)
+            .resizable(true)
+            .collapsible(false)
+            .default_width(680.0)
+            .default_height(460.0)
+            .show(ctx, |ui| {
+                egui::ScrollArea::vertical()
+                    .auto_shrink([false, false])
+                    .show(ui, |ui| {
+                        ui.add(
+                            egui::TextEdit::multiline(&mut content.clone())
+                                .code_editor()
+                                .desired_width(f32::INFINITY)
+                                .interactive(false),
+                        );
+                    });
+            });
+        
+        if !open {
+            self.open_outline_file = None;
+        }
+    }
+}