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/Persistence/WorkoutsModelContainer.swift

@@ -15,7 +15,8 @@ enum WorkoutsModelContainer {
     /// 6: added `deletedLogIDs` to `Workout` (per-log merge deletion tombstones).
     /// 7: renamed `Split` entity to `Routine`.
     /// 8: added `Schedule` cache entity.
-    static let currentSchemaVersion = 8
+    /// 9: added `libraryName` to `Exercise` and `WorkoutLog`.
+    static let currentSchemaVersion = 9
     private static let schemaVersionKey = "Workouts.persistenceSchemaVersion"
     private static let identityTokenKey = "Workouts.iCloudIdentityToken"