Let routines rename exercises and repeat them for interval segments

An exercise's name is now a per-routine display name: a new optional
libraryName on ExerciseDocument (snapshotted onto WorkoutLogDocument at
plan time) keeps the link to the bundled library exercise, and every
figure/info/cue lookup resolves libraryName ?? name. Deliberately not
schema-bumped — an older app dropping the key only strands the
figure link, same rationale as activityType. Cache schema bumped to 9
for the new columns.

The picker no longer filters out exercises already in the routine
(an "×N" badge marks them instead), exercise rows gain a leading
Duplicate swipe that clones an entry in place, and the edit sheet gets
a Name field with the library exercise shown read-only above it.

Claude-Session: https://claude.ai/code/session_01H8VxUX4ckjU3vRF5M4L5FV

Workouts/Views/Routines/RoutineDetailView.swift

@@ -88,6 +88,14 @@ struct RoutineDetailView: View {
                             title: item.name,
                             subtitle: item.planSummary(weightUnit: weightUnit)
                         )
+                        .swipeActions(edge: .leading) {
+                            Button {
+                                duplicateExercise(item)
+                            } label: {
+                                Label("Duplicate", systemImage: "plus.square.on.square")
+                            }
+                            .tint(.teal)
+                        }
                         .swipeActions {
                             Button {
                                 itemToDelete = item
@@ -128,7 +136,11 @@ struct RoutineDetailView: View {
         .sheet(isPresented: $showingExerciseAddSheet) {
             ExercisePickerView(onExerciseSelected: { exerciseNames in
                 addExercises(names: exerciseNames)
-            }, allowMultiSelect: true)
+            }, allowMultiSelect: true,
+               inRoutineCounts: Dictionary(
+                   routine.exercisesArray.map { ($0.libraryExerciseName, 1) },
+                   uniquingKeysWith: +
+               ))
         }
         .sheet(isPresented: $showingRoutineEditSheet) {
             RoutineAddEditView(routine: routine) {
@@ -179,10 +191,8 @@ struct RoutineDetailView: View {
     private func addExercises(names: [String]) {
         guard let routine else { return }
         var doc = RoutineDocument(from: routine)
-        let existingNames = Set(doc.exercises.map { $0.name })
         let base = doc.exercises.count
         let newDocs = names
-            .filter { !existingNames.contains($0) }
             .enumerated()
             .map { i, exName -> ExerciseDocument in
                 // Seed from the library's authored `**Defaults:**` when available,
@@ -215,4 +225,22 @@ struct RoutineDetailView: View {
         doc.updatedAt = Date()
         Task { await sync.save(routine: doc) }
     }
+
+    /// Copy an exercise in place, right after itself — the interval-routine case
+    /// (a treadmill's "Warmup 5 min" / "Brisk Walk 10 min" / … segments all derive
+    /// from the same library exercise). The clone starts out an exact duplicate,
+    /// plan and any customized name included; renaming it is a follow-up edit.
+    private func duplicateExercise(_ exercise: Exercise) {
+        guard let routine else { return }
+        var doc = RoutineDocument(from: routine)
+        guard let idx = doc.exercises.firstIndex(where: { $0.id == exercise.id }) else { return }
+        var copy = doc.exercises[idx]
+        copy.id = ULID.make()
+        doc.exercises.insert(copy, at: idx + 1)
+        for i in doc.exercises.indices {
+            doc.exercises[i].order = i
+        }
+        doc.updatedAt = Date()
+        Task { await sync.save(routine: doc) }
+    }
 }