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+/**
+ * Reconcile cards columns missed by initial-schema backfill (B1 of
+ * reconcile-historical-add-scripts convoy).
+ *
+ * Folds the effects of `scripts/add-card-columns.js` into the migration
+ * history. That historical script ran against every long-lived environment
+ * pre-migration-tool and added two columns to the `cards` table that the
+ * initial-schema backfill (`1779853647564_initial-schema.js`) did NOT
+ * capture in its bootstrap `CREATE TABLE cards`:
+ *
+ *   - cards.quantity   INTEGER  DEFAULT 0
+ *   - cards.favorited  BOOLEAN  DEFAULT false
+ *
+ * Both columns are flagged as "Unused" in docs/SCHEMA_MAP.md § "Known
+ * schema smells" #3 (the live quantity/favorited semantics live on
+ * `user_cards` and `user_favorites`). They are reproduced here verbatim
+ * so a brand-new Neon branch onboarded by `npm run setup-db` ends up
+ * structurally equivalent to prod. The follow-up `drop-dead-cards-columns`
+ * convoy will retire these columns once a query-trace audit confirms zero
+ * readers — see .convoys/reconcile-historical-add-scripts.md § Follow-ups.
+ *
+ * Idempotency (D2): every statement uses `ADD COLUMN IF NOT EXISTS`, so
+ * this migration is safe to run against:
+ *
+ *   (a) A fresh Neon branch where initial-schema just ran → columns do
+ *       not exist → ALTER adds them.
+ *   (b) A long-lived env where `scripts/add-card-columns.js` ran
+ *       pre-migration-tool → columns already exist → ALTER is a no-op
+ *       (only the `pgmigrations` row insert is recorded).
+ *   (c) Re-application of this migration → ALTER is a no-op as in (b).
+ *
+ * Note on overlap with sibling migrations on the `cards` table:
+ *   - `1781440700404_add-scryfall-bulk-columns.js` (PR #32, post-architect
+ *     plan) adds 13 unrelated Scryfall bulk-data columns to `cards`
+ *     (oracle_id, illustration_id, color_identity, keywords, legalities,
+ *     flavor_text, artist, released_at, layout, edhrec_rank, reserved,
+ *     reprint, finishes). Verified to not include quantity/favorited;
+ *     no scope reduction required.
+ *   - `add-updated-at-column.js` (script #7 in the convoy inventory) is
+ *     already fully captured by initial-schema's `updated_at` column on
+ *     `cards` (line 67), so it is intentionally NOT folded here.
+ *
+ * Down-migration is a hard stub. These are reconciliation migrations: the
+ * prod schema state is the source of truth, and rolling back would create
+ * fresh-vs-prod inconsistency. If the columns ever need to be dropped, the
+ * follow-up `drop-dead-cards-columns` convoy will write a new dated
+ * migration with its own real `down()` — do NOT remove this stub.
+ *
+ * @type {import('node-pg-migrate').ColumnDefinitions | undefined}
+ */
+export const shorthands = undefined;
+
+/**
+ * @param {import('node-pg-migrate').MigrationBuilder} pgm
+ * @returns {void}
+ */
+export const up = (pgm) => {
+  pgm.sql(`
+    ALTER TABLE cards
+      ADD COLUMN IF NOT EXISTS quantity INTEGER DEFAULT 0
+  `);
+
+  pgm.sql(`
+    ALTER TABLE cards
+      ADD COLUMN IF NOT EXISTS favorited BOOLEAN DEFAULT false
+  `);
+};
+
+/**
+ * Down-migration is a hard stub. See top-of-file docstring for rationale.
+ *
+ * @returns {void}
+ */
+export const down = () => {
+  throw new Error(
+    '[migration:1781000000001_reconcile-cards-columns] Refusing to drop reconciled cards columns. ' +
+      'This migration folds historical scripts/add-card-columns.js into the migration history; ' +
+      'rolling it back would create fresh-vs-prod schema inconsistency. If cards.quantity / ' +
+      'cards.favorited need to be retired, ship a new dated migration via the queued ' +
+      '`drop-dead-cards-columns` convoy (see .convoys/reconcile-historical-add-scripts.md § Follow-ups).'
+  );
+};