refactor(engine): flatten

- add `just stats`
- add basic doctests

device/track.rs

@@ -1,5 +1,23 @@
 use crate::*;
 
+/// A track consists of a sequencer and zero or more devices chained after it.
+///
+/// ```
+/// let track: tek_device::Track = Default::default();
+/// ```
+#[derive(Debug, Default)] pub struct Track {
+    /// Name of track
+    pub name:      Arc<str>,
+    /// Identifying color of track
+    pub color:     ItemTheme,
+    /// Preferred width of track column
+    pub width:     usize,
+    /// MIDI sequencer state
+    pub sequencer: Sequencer,
+    /// Device chain
+    pub devices:   Vec<Device>,
+}
+
 def_sizes_iter!(TracksSizes => Track);
 
 impl<T: Has<Vec<Track>> + Send + Sync> HasTracks for T {}
@@ -72,20 +90,6 @@ impl<T: MaybeHas<Track>> HasTrack for T {
     }
 }
 
-#[derive(Debug, Default)]
-pub struct Track {
-    /// Name of track
-    pub name:      Arc<str>,
-    /// Identifying color of track
-    pub color:     ItemTheme,
-    /// Preferred width of track column
-    pub width:     usize,
-    /// MIDI sequencer state
-    pub sequencer: Sequencer,
-    /// Device chain
-    pub devices:   Vec<Device>,
-}
-
 has!(Clock:     |self: Track|self.sequencer.clock);
 has!(Sequencer: |self: Track|self.sequencer);
 impl Track {