Refresh the exercise detail screen live on external workout changes

ExerciseView now observes workout.updatedAt and pulls the latest doc/progress
from the cache, mirroring WorkoutLogListView. A set completed on the watch now
advances the iPhone set grid in real time instead of only on re-entry.

Claude-Session: https://claude.ai/code/session_018gg69MaUetDNzWzBXisfMV

Workouts/Views/WorkoutLogs/ExerciseView.swift

@@ -63,6 +63,20 @@ struct ExerciseView: View {
             refreshDocIfNeeded()
             progress = log?.currentStateIndex ?? 0
         }
+        // Reflect external changes (e.g. a set completed on the watch) live. Each edit
+        // rewrites the whole workout file, so the cache always holds the latest — pulling
+        // it in can't revert a newer local tap.
+        .onChange(of: workout.updatedAt) { _, _ in
+            absorbExternalUpdate()
+        }
+    }
+
+    /// Pull an externally-changed workout into the working copy so the set grid and plan
+    /// update without leaving and re-entering the screen.
+    private func absorbExternalUpdate() {
+        let fresh = WorkoutDocument(from: workout)
+        doc = fresh
+        progress = fresh.logs.first(where: { $0.id == logID })?.currentStateIndex ?? progress
     }
 
     @ViewBuilder