Guard plan drafts against swaps and keep confirm on single-flight

Return the draft job id as jobId, as the plan API contract specifies.

Add a week_plans revision (migration 0013) that every swap and stored
draft raises. A draft_week job reads the revision before draft_week runs
and stores its week only while the plan still has it; a plan edited
while the AI ran is left as it is and the job fails plan_changed, so a
draft never erases the household's swap.

A confirmed draft now joins only a confirmed queued or running job, so a
job asked for without confirm can no longer fail it with
confirm_required after the plan was synced.

Test simultaneous drafts, a swap during a draft, a confirmed draft while
an unconfirmed one runs, impossible calendar dates and start_by across
the end of daylight saving time.

Maestro task ea48e650-d510-49cc-8485-0f07174ee731.

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

migrations/queries/plans.sql

@@ -18,9 +18,10 @@ INSERT INTO week_plans (id, week_start, status, ai_note, created_at, updated_at)
 VALUES (?, ?, 'draft', ?, ?, ?);
 
 -- name: RedraftWeekPlan :exec
--- Records a new draft over plan id: its status and note.
+-- Records a new draft over plan id: its status and note, raising its
+-- revision.
 UPDATE week_plans
-SET status = ?, ai_note = ?, updated_at = ?
+SET status = ?, ai_note = ?, revision = revision + 1, updated_at = ?
 WHERE id = ?;
 
 -- name: PutPlanDay :exec
@@ -39,10 +40,11 @@ SET dinner_id = ?, is_new = ?, updated_at = ?
 WHERE plan_id = ? AND date = ?;
 
 -- name: MarkWeekPlanEdited :exec
--- Records an edit of plan id: a synced plan becomes changed, any other
--- keeps its status.
+-- Records an edit of plan id, raising its revision: a synced plan becomes
+-- changed, any other keeps its status.
 UPDATE week_plans
 SET status = CASE WHEN status = 'synced' THEN 'changed' ELSE status END,
+	revision = revision + 1,
 	updated_at = ?
 WHERE id = ?;
 
@@ -72,10 +74,12 @@ ORDER BY plan_days.date;
 
 -- name: GetActiveDraftJobID :one
 -- The id of the job of kind queued or running for the week starting
--- week_start. Returns sql.ErrNoRows when there is none.
+-- week_start, one whose payload has confirm when confirmed is 1. Returns
+-- sql.ErrNoRows when there is none.
 SELECT id FROM jobs
 WHERE kind = sqlc.arg(kind)
 	AND status IN ('queued', 'running')
 	AND json_extract(payload, '$.week_start') = sqlc.arg(week_start)
+	AND (CAST(sqlc.arg(confirmed) AS INTEGER) = 0 OR json_extract(payload, '$.confirm') = 1)
 ORDER BY id
 LIMIT 1;