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/Documents.swift

@@ -29,6 +29,12 @@ struct SplitDocument: Codable, Sendable, Equatable, Identifiable {
     /// older app dropping it on rewrite (reverting to the default) is preferable to
     /// quarantining the user's whole routine.
     var activityType: Int?
+    /// Per-split rest length (seconds) and flow-mode toggle. Both optional and
+    /// deliberately NOT schema-bumped, same rationale as `activityType`: an older
+    /// app dropping them on rewrite reverts to the global default rest / no-flow,
+    /// which is preferable to quarantining the user's whole routine.
+    var restSeconds: Int? = nil
+    var autoAdvance: Bool? = nil
 
     // Bumped 1→2 when the weight-reminder fields (`weightLastUpdated`,
     // `weightReminderWeeks`) and `category` were removed and `machineSettings` was
@@ -103,6 +109,13 @@ struct WorkoutDocument: Codable, Sendable, Equatable, Identifiable {
     /// period. See `WorkoutMergePlanner`.
     var deletedLogIDs: [String: Date]? = nil
 
+    /// Snapshot of the split's rest length / flow flag at plan time (a running
+    /// workout has no live link to its split, same reason sets/reps/weight are
+    /// snapshotted per log). Optional and not schema-bumped, same rationale as
+    /// `SplitDocument.restSeconds`/`autoAdvance`.
+    var restSeconds: Int? = nil
+    var autoAdvance: Bool? = nil
+
     // Bumped 1→2 when `metrics` was added: the captured HR/calorie data is
     // irreplaceable, so the forward-gate must quarantine these files on older apps
     // rather than let them strip `metrics` on rewrite.

Shared/Model/Entities.swift

@@ -24,6 +24,8 @@ final class Split {
     var updatedAt: Date = Date()
     var jsonRelativePath: String = ""
     var activityTypeRaw: Int = 0
+    var restSeconds: Int?
+    var autoAdvance: Bool?
 
     @Relationship(deleteRule: .cascade, inverse: \Exercise.split)
     var exercises: [Exercise] = []
@@ -148,6 +150,8 @@ final class Workout {
     /// phone re-derives them into any `WorkoutDocument` it rebuilds and the merge stays
     /// deletion-safe across cache round-trips. Phone-authored; see `WorkoutMergePlanner`.
     var deletedLogIDs: [String: Date]?
+    var restSeconds: Int?
+    var autoAdvance: Bool?
 
     @Relationship(deleteRule: .cascade, inverse: \WorkoutLog.workout)
     var logs: [WorkoutLog] = []

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>()