Add machine comfort settings and tighten the document schemas

Machine-based exercises now carry ordered name/value comfort settings
(seat height, back-rest position, ...) on both ExerciseDocument and, as a
plan-time snapshot, WorkoutLogDocument — the optional array doubles as the
machine flag. Editable from the exercise editor's new Machine section and
from the workout row's settings sheet, whose mid-workout edits write back
to the originating split (workout saved first, so seed clone-on-edit
repointing can't clobber the log edit).

Schema tightening rides the same rev: splits bump to v2 (weight-reminder
fields and the unused exercise category removed), workouts to v3 (the
derived `completed` flag removed; status is the single source). Starter
seeds regenerated at v2 with unchanged ULIDs; SwiftData cache schema
bumped to rebuild. SCHEMA.md documents the shapes.

Claude-Session: https://claude.ai/code/session_01LEoff8bXGBS83tK1c55Mf7

Workouts/Views/Exercises/ExerciseListView.swift

@@ -226,14 +226,7 @@ struct ExerciseListView: View {
         guard let split else { return }
         let startDate = Date()
         let logs = split.exercisesArray.enumerated().map { i, ex in
-            WorkoutLogDocument(
-                id: ULID.make(), exerciseName: ex.name, order: i,
-                sets: ex.sets, reps: ex.reps, weight: ex.weight,
-                loadType: ex.loadType, durationSeconds: ex.durationTotalSeconds,
-                currentStateIndex: 0, completed: false,
-                status: WorkoutStatus.notStarted.rawValue,
-                notes: nil, date: startDate
-            )
+            WorkoutLogDocument(planFrom: ExerciseDocument(from: ex), order: i, date: startDate)
         }
         let doc = WorkoutDocument(
             schemaVersion: WorkoutDocument.currentSchemaVersion,
@@ -266,7 +259,7 @@ struct ExerciseListView: View {
                     id: ULID.make(), name: exName, order: base + i,
                     sets: 3, reps: 10, weight: 40,
                     loadType: LoadType.weight.rawValue,
-                    durationSeconds: 0, weightLastUpdated: nil, weightReminderWeeks: 2
+                    durationSeconds: 0
                 )
             }
         doc.exercises.append(contentsOf: newDocs)