Merge watch workout pushes per log instead of whole-document

ingestFromWatch arbitrated by whole-document updatedAt, so concurrent edits
to the same workout on both devices (phone edits exercise A while the watch
completes exercise B) lost one side wholesale — the newer snapshot replaced
the other (H1).

Reconcile per log instead. WorkoutMergePlanner (pure, deterministic) unions
logs by id, resolves each by newest per-log updatedAt, and applies
phone-authored deletion tombstones so an absent log is never ambiguous
between "deleted on the phone" and "just added on the watch". Edits to
different exercises now commute — delivery order and offline gaps stop
mattering. A stale/duplicate push merges back to exactly the cached doc, so
ingest re-pushes authoritative state rather than writing.

The per-log updatedAt scaffolding shipped (unused) in schema v4; it's now
stamped by transition(to:) on status flips and a new touch() at the
content-only edit sites (order, notes, machine settings, adjusted entries,
new logs) on both phone and watch. deletedLogIDs is new: additive on the
wire and cache, phone-authored (deleteLog), pruned after a 30-day grace.
Because an older build rewriting a file would strip the tombstones and
resurrect a deleted exercise, WorkoutDocument schema bumps 4->5 (forward
gate quarantines old builds) and the cache bumps 5->6.

recomputeStatusFromLogs takes an injectable now: so the merge recomputes
status/end deterministically. WorkoutMergePlannerTests pins the decision
table (commute, per-log newer-wins, legacy-nil, watch-add, tombstone
honored/resurrect/union/prune, status recompute, no-op re-push);
WorkoutDocumentMapperTests gains the deletedLogIDs round-trip.

Workouts/Views/WorkoutLogs/ExerciseProgressView.swift

@@ -605,6 +605,7 @@ struct ExerciseProgressView: View {
         guard let i = doc.logs.firstIndex(where: { $0.id == logID }),
               let last = doc.logs[i].setEntries?.indices.last else { return }
         doc.logs[i].setEntries?[last] = entry
+        doc.logs[i].touch()
         doc.updatedAt = Date()
         onChange()
     }

Workouts/Views/WorkoutLogs/ExerciseView.swift

@@ -191,6 +191,7 @@ struct ExerciseView: View {
     private func applyMachineSettings(_ settings: [MachineSetting]) {
         guard let i = doc.logs.firstIndex(where: { $0.id == logID }) else { return }
         doc.logs[i].machineSettings = settings
+        doc.logs[i].touch()
         doc.updatedAt = Date()
         let snapshot = doc
         let exerciseName = doc.logs[i].exerciseName

Workouts/Views/WorkoutLogs/NotesEditView.swift

@@ -51,6 +51,7 @@ struct NotesEditView: View {
         var doc = WorkoutDocument(from: workout)
         guard let i = doc.logs.firstIndex(where: { $0.id == logID }) else { return }
         doc.logs[i].notes = notesText
+        doc.logs[i].touch()
         doc.updatedAt = Date()
         let snapshot = doc
         Task { await sync.save(workout: snapshot) }

Workouts/Views/WorkoutLogs/PlanEditView.swift

@@ -158,6 +158,7 @@ struct PlanEditView: View {
         doc.logs[i].weight = Double(weight)
         doc.logs[i].durationSeconds = totalSeconds
         doc.logs[i].loadType = selectedLoadType.rawValue
+        doc.logs[i].touch()
         doc.updatedAt = Date()
         let exerciseName = doc.logs[i].exerciseName
         let workoutDoc = doc

Workouts/Views/WorkoutLogs/WorkoutLogListView.swift

@@ -294,6 +294,9 @@ struct WorkoutLogListView: View {
     private func deleteLog(_ log: WorkoutLogDocument) {
         withAnimation {
             doc.logs.removeAll { $0.id == log.id }
+            // Tombstone the deletion so a stale watch push still carrying this log can't
+            // resurrect it — the per-log merge drops a tombstoned id (see WorkoutMergePlanner).
+            doc.deletedLogIDs = (doc.deletedLogIDs ?? [:]).merging([log.id: Date()]) { _, new in new }
             save()
         }
     }
@@ -302,8 +305,9 @@ struct WorkoutLogListView: View {
         var logs = sortedLogs
         logs.move(fromOffsets: source, toOffset: destination)
         for (index, log) in logs.enumerated() {
-            if let i = doc.logs.firstIndex(where: { $0.id == log.id }) {
+            if let i = doc.logs.firstIndex(where: { $0.id == log.id }), doc.logs[i].order != index {
                 doc.logs[i].order = index
+                doc.logs[i].touch()
             }
         }
         save()
@@ -333,7 +337,8 @@ struct WorkoutLogListView: View {
         }
         doc.end = nil
 
-        let newLog = WorkoutLogDocument(planFrom: plan, order: doc.logs.count, date: now)
+        var newLog = WorkoutLogDocument(planFrom: plan, order: doc.logs.count, date: now)
+        newLog.touch(now)   // a fresh log carries a definite creation time for the merge
         doc.logs.append(newLog)
         save()
 
@@ -389,6 +394,7 @@ struct WorkoutLogListView: View {
     private func applyMachineSettings(_ settings: [MachineSetting], toLogID id: String) {
         guard let i = doc.logs.firstIndex(where: { $0.id == id }) else { return }
         doc.logs[i].machineSettings = settings
+        doc.logs[i].touch()
         doc.recomputeStatusFromLogs()
         doc.updatedAt = Date()