Revalidate the draft pool on save, refuse duplicate swaps, refresh the Quest log after a draft

Feature 14 integration fix (Maestro 857e4c33-e250-46ec-b5ea-7dd4f3b719d9).

- F14-01: storeDraft re-reads the draft pool (ListDraftPool, the same
  eligibility rule draft_week was given) inside the save transaction. A
  day whose dinner was archived, moved to tried, or planned on another
  current or later week while draft_week ran fails the job with the new
  retryable reason pool_changed and stores nothing.
- F14-02: Swap refuses a dinner already on another day of the week inside
  the write transaction; the API answers 409 dinner_already_planned.
- F14-03: a finished draft invalidates the Quest log query, as the swap
  path does, so the tablet strip and desktop panel drop dinners it planned.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/plan/plan.go

@@ -53,10 +53,15 @@ const (
 	// ReasonPlanChanged: the plan was edited while draft_week ran, so the
 	// draft does not replace the edit.
 	ReasonPlanChanged = "plan_changed"
+	// ReasonPoolChanged: a dinner the draft planned left the pool while
+	// draft_week ran (archived, tried, or its Quest log dinner planned on
+	// another week), so the draft is not stored; drafting again uses the
+	// pool as it is now.
+	ReasonPoolChanged = "pool_changed"
 )
 
 // Reasons are every draft failure reason.
-var Reasons = []string{ReasonNotEnoughDinners, ReasonAIFailed, ReasonConfirmRequired, ReasonPlanChanged}
+var Reasons = []string{ReasonNotEnoughDinners, ReasonAIFailed, ReasonConfirmRequired, ReasonPlanChanged, ReasonPoolChanged}
 
 // ContextBudget is the character budget of the household context
 // draft_week is given (see harness.BuildContext).
@@ -71,6 +76,10 @@ var ErrNotFound = errors.New("plan not found")
 // ErrDinnerNotFound is a swap to an unknown dinner.
 var ErrDinnerNotFound = errors.New("dinner not found")
 
+// ErrDinnerAlreadyPlanned is a swap to a dinner already on another day of
+// the week.
+var ErrDinnerAlreadyPlanned = errors.New("the dinner is already on another day of this week")
+
 // ErrConfirmRequired is a draft over a synced or changed plan asked for
 // without confirm.
 var ErrConfirmRequired = errors.New("the plan was pushed to Calendar; drafting over it needs confirm")
@@ -337,9 +346,10 @@ func (s *Service) StartDraft(ctx context.Context, weekStart store.LocalDate, con
 // Swap plans dinnerID on date of the week starting weekStart, marking the
 // day new when the dinner is in the Quest log. Swapping a synced plan
 // makes it changed. The week must have a plan (else ErrNotFound), date
-// must be one of its days (else *InvalidDayError), and the dinner must be
-// a Regular or in the Quest log (else ErrDinnerNotFound or
-// *DinnerNotPlannableError). It returns the plan as swapped.
+// must be one of its days (else *InvalidDayError), the dinner must be a
+// Regular or in the Quest log (else ErrDinnerNotFound or
+// *DinnerNotPlannableError), and it must not be on another day of the
+// week (else ErrDinnerAlreadyPlanned). It returns the plan as swapped.
 func (s *Service) Swap(ctx context.Context, weekStart store.LocalDate, date, dinnerID string) (Plan, error) {
 	dates, err := household.WeekDays(weekStart)
 	if err != nil {
@@ -369,6 +379,13 @@ func (s *Service) Swap(ctx context.Context, weekStart store.LocalDate, date, din
 		if !slices.Contains(plannable, d.Status) {
 			return &DinnerNotPlannableError{Status: d.Status}
 		}
+		days, err := q.ListPlanDays(ctx, cur.ID)
+		if err != nil {
+			return fmt.Errorf("plan: read days of %s: %w", cur.ID, err)
+		}
+		if slices.ContainsFunc(days, func(r db.ListPlanDaysRow) bool { return r.Date != day.String() && r.Dinner.ID == d.ID }) {
+			return ErrDinnerAlreadyPlanned
+		}
 		now := store.Now().String()
 		n, err := q.SwapPlanDay(ctx, db.SwapPlanDayParams{
 			DinnerID:  sql.NullString{String: d.ID, Valid: true},