chore: update app initialization and example data

Update application initialization and example data.

- `App::new` now recomputes formulas on startup to ensure formula-derived
  values are available immediately.
- Updated `examples/demo.improv` to reflect changes in formula and category
  structure.

Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/gemma-4-26B-A4B-it-GGUF:UD-Q5_K_XL)

src/ui/app.rs

@@ -199,7 +199,16 @@ pub struct App {
 }
 
 impl App {
-    pub fn new(model: Model, file_path: Option<PathBuf>) -> Self {
+    pub fn new(mut model: Model, file_path: Option<PathBuf>) -> Self {
+        // Recompute formula cache before building the initial layout so
+        // formula-derived values are available on the first frame.
+        let none_cats: Vec<String> = model
+            .active_view()
+            .categories_on(crate::view::Axis::None)
+            .into_iter()
+            .map(String::from)
+            .collect();
+        model.recompute_formulas(&none_cats);
         let layout = {
             let view = model.active_view();
             GridLayout::with_frozen_records(&model, view, None)