Open new workouts directly and improve accessibility

Starting a workout — from the split picker or a split's exercise list —
now drops straight into its log screen once the cache catches up, via a
shared StartedWorkoutNavigator. Adds VoiceOver labels/values to the log
checkboxes and the settings button, a color-independent numbered legend
and spoken summary to the heart-rate-zone bar, and Dynamic Type scaling
to the run-flow badges and timer.

Claude-Session: https://claude.ai/code/session_01HJDQQDA9QdP8zByg43H5v3

Workouts/ExerciseFigure/ExerciseFigureView.swift

@@ -89,8 +89,9 @@ struct ExerciseFigureView: View {
                 draw(&ctx, size: size, time: context.date.timeIntervalSinceReferenceDate)
             }
         }
-        .accessibilityLabel("Animated form guide")
-        .accessibilityHidden(false)
+        // Purely decorative: the paged flow already conveys the exercise and its
+        // progress, so the looping figure is skipped by VoiceOver.
+        .accessibilityHidden(true)
     }
 
     private func draw(_ ctx: inout GraphicsContext, size: CGSize, time: Double) {