Record per-set actuals and drive the chart and volume from them

Every completed set now writes a SetEntry (reps/weight or seconds),
pre-filled from the plan by transition(to:) so the list checkbox, both
run flows, and One More all capture for free; reset clears, skip keeps
partials. The rest and finish pages show the just-done set as a pill
that opens a stepper sheet for correcting reps and weight (2.5 lb /
1.25 kg steps). The Weight Progression chart plots the top-set actual
weight and workout volume sums recorded sets, both falling back to the
plan for legacy logs via effectiveSetEntries.

Storage side of UX #3 rides along: plan weights are Double now.
Schema bumps: SplitDocument 2→3, WorkoutDocument 3→4 (a fractional
weight fails an older Int decode, and a rewrite would strip the
irreplaceable actuals), SwiftData cache 4→5. A per-log updatedAt is
reserved for the future cross-device log merge.

Claude-Session: https://claude.ai/code/session_01HJDQQDA9QdP8zByg43H5v3

Workouts/Views/WorkoutLogs/PlanEditView.swift

@@ -136,7 +136,9 @@ struct PlanEditView: View {
                 if let log = WorkoutDocument(from: workout).logs.first(where: { $0.id == logID }) {
                     sets = log.sets
                     reps = log.reps
-                    weight = log.weight
+                    // The picker steps whole values; a fractional stored weight
+                    // shows (and saves back) its whole part until UX #3's UI lands.
+                    weight = Int(log.weight)
                     durationMinutes = log.durationSeconds / 60
                     durationSeconds = log.durationSeconds % 60
                     selectedLoadType = LoadType(rawValue: log.loadType) ?? .weight
@@ -153,7 +155,7 @@ struct PlanEditView: View {
         guard let i = doc.logs.firstIndex(where: { $0.id == logID }) else { return }
         doc.logs[i].sets = sets
         doc.logs[i].reps = reps
-        doc.logs[i].weight = weight
+        doc.logs[i].weight = Double(weight)
         doc.logs[i].durationSeconds = totalSeconds
         doc.logs[i].loadType = selectedLoadType.rawValue
         doc.updatedAt = Date()
@@ -170,7 +172,7 @@ struct PlanEditView: View {
             if let ei = sDoc.exercises.firstIndex(where: { $0.name == exerciseName }) {
                 sDoc.exercises[ei].sets = sets
                 sDoc.exercises[ei].reps = reps
-                sDoc.exercises[ei].weight = weight
+                sDoc.exercises[ei].weight = Double(weight)
                 sDoc.exercises[ei].durationSeconds = totalSeconds
                 sDoc.exercises[ei].loadType = selectedLoadType.rawValue
                 sDoc.updatedAt = Date()