Clamp the progress gauge ratio

The player position can overrun a stale or wrong duration (streams,
hand-written track files), and ratatui's LineGauge asserts its ratio
into 0..=1 — the TUI died with "ratio should be between 0 and 1"
mid-playback. Clamp instead, with render regression tests for both the
overrun and the zero-duration case.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

cbd-tui/src/app/now_playing.rs

@@ -142,10 +142,16 @@ impl NowPlaying {
                 .constraints([Constraint::Min(10), Constraint::Max(completion_size)])
                 .split(now_playing_layout[1]);
 
+            // Clamped: the player's position can overrun a stale or wrong
+            // duration (streams, hand-written track files), and
+            // `LineGauge` panics on ratios outside 0..=1.
             let ratio = if duration.is_zero() {
                 0.0
             } else {
-                position.as_secs_f64().div(duration.as_secs_f64())
+                position
+                    .as_secs_f64()
+                    .div(duration.as_secs_f64())
+                    .clamp(0.0, 1.0)
             };
 
             let progress = LineGauge::default()
@@ -180,3 +186,48 @@ impl NowPlaying {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use ratatui::{backend::TestBackend, Terminal};
+
+    /// A now-playing pane mid-track, built directly (no `update_track`,
+    /// which fires a desktop notification).
+    fn now_playing(position_ms: u32, duration_ms: u32) -> NowPlaying {
+        NowPlaying {
+            play_state: PlayState::Playing,
+            duration: Some(Duration::from_millis(duration_ms.into())),
+            modifiers: QueueModifiers::default(),
+            position: Some(Duration::from_millis(position_ms.into())),
+            track: Some(Track {
+                path: "/fs/radio.cbd-track.toml".to_string(),
+                artist: "artist".to_string(),
+                title: "title".to_string(),
+                duration: None,
+                album: None,
+            }),
+        }
+    }
+
+    fn render(pane: &NowPlaying) {
+        let backend = TestBackend::new(60, 12);
+        let mut terminal = Terminal::new(backend).expect("test terminal");
+        terminal
+            .draw(|f| pane.render(f, f.area()))
+            .expect("draw must not panic");
+    }
+
+    /// The position can overrun a stale or wrong duration (streams,
+    /// hand-written track files); the gauge must clamp instead of hitting
+    /// ratatui's `ratio should be between 0 and 1` panic.
+    #[test]
+    fn progress_gauge_survives_position_past_duration() {
+        render(&now_playing(90_000, 60_000));
+    }
+
+    #[test]
+    fn progress_gauge_survives_a_zero_duration() {
+        render(&now_playing(5_000, 0));
+    }
+}