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

Shared/Model/Documents.swift

@@ -71,6 +71,19 @@ struct ExerciseDocument: Codable, Sendable, Equatable, Identifiable {
     /// empty → a machine exercise with nothing recorded yet. This optionality
     /// doubles as the machine-based flag — there is no separate Bool.
     var machineSettings: [MachineSetting]? = nil
+    /// The library exercise `name` was customized from (e.g. "Treadmill" renamed to
+    /// "Brisk Walk 10 min" for one segment of an interval routine); nil → `name` IS
+    /// the library name. Optional and deliberately NOT schema-bumped, same rationale
+    /// as `RoutineDocument.activityType`: an older app dropping it on rewrite only
+    /// strands the figure/info link for the renamed exercise, which is preferable to
+    /// quarantining the user's whole routine.
+    var libraryName: String? = nil
+}
+
+extension ExerciseDocument {
+    /// The name to resolve figure/info/cues against — `name` itself unless it was
+    /// customized, in which case the library exercise it derives from.
+    var libraryExerciseName: String { libraryName ?? name }
 }
 
 /// A single free-form comfort setting for a machine-based exercise. `value` is a
@@ -251,9 +264,18 @@ struct WorkoutLogDocument: Codable, Sendable, Equatable, Identifiable {
     /// on two devices merges by the newer `updatedAt`). Nothing writes it yet;
     /// absent in older files.
     var updatedAt: Date? = nil
+    /// Plan-time snapshot of the exercise's `libraryName` (like sets/reps/weight).
+    /// Optional and deliberately NOT schema-bumped, same rationale as
+    /// `RoutineDocument.activityType`: an older app dropping it on rewrite only
+    /// strands the figure/info link for a renamed exercise, which is preferable to
+    /// quarantining the whole workout.
+    var libraryName: String? = nil
 }
 
 extension WorkoutLogDocument {
+    /// The name to resolve figure/info/cues against — see `ExerciseDocument.libraryExerciseName`.
+    var libraryExerciseName: String { libraryName ?? exerciseName }
+
     /// Build a fresh plan-time log from a routine's exercise. Snapshots the plan
     /// fields (sets/reps/weight/duration) *and* the machine comfort settings, so a
     /// running workout carries the exercise's settings as its own editable copy —
@@ -274,7 +296,8 @@ extension WorkoutLogDocument {
             status: WorkoutStatus.notStarted.rawValue,
             notes: nil,
             date: date,
-            machineSettings: exercise.machineSettings
+            machineSettings: exercise.machineSettings,
+            libraryName: exercise.libraryName
         )
     }