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

Shared/HealthKit/HealthKitMapping.swift

@@ -28,13 +28,21 @@ extension WorkoutActivityType {
     }
 }
 
-/// Σ sets×reps×weight across weighted logs — the app-native "how much work" number.
+/// Σ reps×weight across weighted logs — the app-native "how much work" number.
 /// Computed in the stored weight unit (display-only units never change the value).
+/// Sums recorded per-set actuals when a log has them (via `effectiveSetEntries`,
+/// which also synthesizes plan entries for completed legacy logs — identical to
+/// the old sets×reps×weight formula); a legacy log with no entries at all falls
+/// back to that plan formula unchanged.
 enum WorkoutVolume {
     static func total(_ logs: [WorkoutLogDocument]) -> Double {
         logs.reduce(0) { sum, log in
             guard LoadType(rawValue: log.loadType) == .weight else { return sum }
-            return sum + Double(log.sets * log.reps * log.weight)
+            let entries = log.effectiveSetEntries
+            guard !entries.isEmpty else {
+                return sum + Double(log.sets * log.reps) * log.weight
+            }
+            return sum + entries.reduce(0) { $0 + Double($1.reps ?? 0) * ($1.weight ?? 0) }
         }
     }
 }