Improve indeterminate installer progress bar animation (#163)

* Improve indeterminate progress bar animation

Refactor indeterminate progress bar rendering for smoother animation.

* progress: rustfmt, and skip the wrapped segment while it's off the track

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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Co-authored-by: Brandon Thomas <echelon@gmail.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

crates/ui-egui/src/widgets.rs

@@ -400,14 +400,16 @@ pub fn progress(ui: &mut Ui, fraction: Option<f32>, caption: &str, color: Color3
             p.rect_filled(Rect::from_min_size(bar.min, vec2(bar.width() * f.clamp(0.0, 1.0), bar.height())), CornerRadius::ZERO, color);
         }
         None => {
-            // Indeterminate: a sweeping segment.
-            let x = (ui.input(|i| i.time) as f32 * 0.8).fract();
-            let seg = Rect::from_min_size(
-                egui::pos2(bar.left() + bar.width() * (x * 1.3 - 0.3).max(0.0), bar.top()),
-                vec2(bar.width() * 0.3, bar.height()),
-            )
-            .intersect(bar);
-            p.rect_filled(seg, CornerRadius::ZERO, color);
+            // Keep the segment moving through the track boundary without resetting visibly.
+            let width = bar.width();
+            let segment_width = width * 0.3;
+            let x = (ui.input(|i| i.time) * 0.8).fract() as f32 * width;
+            for left in [x, x - width] {
+                let seg = Rect::from_min_size(egui::pos2(bar.left() + left, bar.top()), vec2(segment_width, bar.height())).intersect(bar);
+                if seg.is_positive() {
+                    p.rect_filled(seg, CornerRadius::ZERO, color);
+                }
+            }
             ui.ctx().request_repaint();
         }
     }