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+/**
+ * Reconcile collaboration tables missed by the initial-schema backfill.
+ *
+ * Captures the DDL half of `scripts/add-collaboration-features.js` (a
+ * historical no-go-zone script) that the `initial-schema` backfill missed:
+ *
+ *   1. `collection_permissions` (collaboration roles + invite tokens)
+ *   2. `collection_activity` (audit-trail with JSONB details)
+ *   3. `users.is_pending` (column for invited-but-not-yet-accepted users)
+ *   4. 4 indexes for query hot-paths
+ *
+ * `lib/permission-middleware.js` reads `collection_permissions` in
+ * `withCollectionPermission` and writes `collection_activity` from
+ * `logCollectionActivity` — both are runtime invariants, so a fresh Neon
+ * branch onboarded by `npm run setup-db` MUST land these tables. Prod was
+ * brought to this shape by `add-collaboration-features.js` running
+ * historically; this migration brings fresh envs to parity per
+ * `.convoys/reconcile-historical-add-scripts.md` § Brief outline → B3.
+ *
+ * Idempotent against:
+ *   - A brand-new Neon branch (creates everything fresh).
+ *   - Any long-lived env where `add-collaboration-features.js` already ran
+ *     (every CREATE TABLE / ADD COLUMN / CREATE INDEX is `IF NOT EXISTS`-
+ *     guarded → no-op except recording the `pgmigrations` row).
+ *
+ * The owner-permission DML backfill from the historical script is NOT
+ * captured: a fresh env has no pre-existing collections needing
+ * back-fill, and prod's backfill is already applied.
+ *
+ * @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(`
+    CREATE TABLE IF NOT EXISTS collection_permissions (
+      id SERIAL PRIMARY KEY,
+      collection_id INTEGER REFERENCES collections(id) ON DELETE CASCADE,
+      user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
+      role VARCHAR(20) NOT NULL CHECK (role IN ('owner', 'editor', 'viewer')),
+      status VARCHAR(20) DEFAULT 'active' CHECK (status IN ('active', 'pending', 'declined')),
+      invite_token VARCHAR(255) UNIQUE,
+      invited_by INTEGER REFERENCES users(id),
+      created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+      updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+      UNIQUE(collection_id, user_id)
+    )
+  `);
+
+  pgm.sql(`
+    CREATE TABLE IF NOT EXISTS collection_activity (
+      id SERIAL PRIMARY KEY,
+      collection_id INTEGER REFERENCES collections(id) ON DELETE CASCADE,
+      user_id INTEGER REFERENCES users(id) ON DELETE SET NULL,
+      action VARCHAR(50) NOT NULL,
+      details JSONB,
+      created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+    )
+  `);
+
+  pgm.sql(`
+    ALTER TABLE users
+    ADD COLUMN IF NOT EXISTS is_pending BOOLEAN DEFAULT false
+  `);
+
+  pgm.sql(`
+    CREATE INDEX IF NOT EXISTS idx_collection_permissions_collection_id
+      ON collection_permissions(collection_id);
+    CREATE INDEX IF NOT EXISTS idx_collection_permissions_user_id
+      ON collection_permissions(user_id);
+    CREATE INDEX IF NOT EXISTS idx_collection_activity_collection_id
+      ON collection_activity(collection_id);
+    CREATE INDEX IF NOT EXISTS idx_collections_visibility
+      ON collections(visibility);
+  `);
+};
+
+/**
+ * Down-migration is a hard stub. Dropping `collection_permissions` /
+ * `collection_activity` would erase every collaboration role assignment
+ * and every audit-trail row in the database; dropping `users.is_pending`
+ * would discard the invited-user state for every pending invite. If a
+ * future schema correction needs to mutate one of these surfaces, write a
+ * NEW dated migration with a real `down` — do NOT remove this stub.
+ *
+ * @returns {void}
+ */
+export const down = () => {
+  throw new Error(
+    '[migration:1781000000003_reconcile-collaboration-tables] Refusing to drop ' +
+      'collection_permissions / collection_activity / users.is_pending. Rolling back ' +
+      'this migration would erase every collaboration role assignment, every audit-trail ' +
+      'row, and every invited-user pending state in the database. If you need a clean ' +
+      'schema for testing, branch the Neon database and run `npm run migrate up` against ' +
+      'the branch instead.'
+  );
+};