Add per-split rest length and hands-free auto-advance flow

Two per-split settings, with the global Settings values as defaults:

- restSeconds: Int? — per-split rest, used between sets and (in flow) between
  exercises; nil falls back to the global default.
- autoAdvance: Bool? — flow mode: finishing an exercise rests, then opens the
  next one hands-free, all the way through the split.

Both are optional, snapshotted onto WorkoutDocument at the start sites (no live
split link), and not schema-bumped — same degradation pattern as activityType.

A thin RunFlowView wrapper (iOS + watch) owns the on-screen log and swaps it via
.id(currentLogID) on hand-off, so the per-exercise ExerciseProgressView stays
per-logID and untouched; the between-exercise rest reuses the existing .rest
countdown as the terminal page. The mirror reuses the per-logID live channel:
the wrapper suppresses the boundary .ended teardown so it follows across
exercises, and ContentView re-keys the cover on frame.logID — no sync-bridge
changes.

Morning Wake-Up ships as a flowing 45s-work / 15s-rest routine.

New Rest & Pacing section in the split editor exposes both controls.

Shared/Model/Mappers.swift

@@ -27,7 +27,8 @@ extension SplitDocument {
                   color: split.color, systemImage: split.systemImage, order: split.order,
                   createdAt: split.createdAt, updatedAt: split.updatedAt,
                   exercises: split.exercisesArray.map(ExerciseDocument.init(from:)),
-                  activityType: split.activityTypeRaw)
+                  activityType: split.activityTypeRaw,
+                  restSeconds: split.restSeconds, autoAdvance: split.autoAdvance)
     }
 }
 
@@ -50,7 +51,8 @@ extension WorkoutDocument {
                   status: workout.statusRaw, createdAt: workout.createdAt, updatedAt: workout.updatedAt,
                   logs: workout.logsArray.map(WorkoutLogDocument.init(from:)),
                   metrics: workout.metrics,
-                  deletedLogIDs: workout.deletedLogIDs)
+                  deletedLogIDs: workout.deletedLogIDs,
+                  restSeconds: workout.restSeconds, autoAdvance: workout.autoAdvance)
     }
 }
 
@@ -89,6 +91,8 @@ enum CacheMapper {
         split.updatedAt = doc.updatedAt
         split.jsonRelativePath = relativePath
         split.activityTypeRaw = doc.activityType ?? 0
+        split.restSeconds = doc.restSeconds
+        split.autoAdvance = doc.autoAdvance
 
         let existing = Dictionary(split.exercises.map { ($0.id, $0) }, uniquingKeysWith: { a, _ in a })
         var keep = Set<String>()
@@ -147,6 +151,8 @@ enum CacheMapper {
         workout.jsonRelativePath = relativePath
         workout.metrics = doc.metrics
         workout.deletedLogIDs = doc.deletedLogIDs
+        workout.restSeconds = doc.restSeconds
+        workout.autoAdvance = doc.autoAdvance
 
         let existing = Dictionary(workout.logs.map { ($0.id, $0) }, uniquingKeysWith: { a, _ in a })
         var keep = Set<String>()