fix(db): migrator introspects only the target schema

Kysely's Migrator checks for its tables via introspection.getTables(),
which reflects every schema and calls has_schema_privilege /
pg_get_serial_sequence per schema. When another test file drops its schema
at the same moment those functions fail with "schema … does not exist" —
the intermittent server PG test failures on the shared dev database.
createMigrator now hands the Migrator a proxy whose introspection only
looks at the migration schema (or current_schema()). A regression test
churns schemas while migrating; it fails on the old migrator.

Also samples EngineRunQuery's comma-separated status/triggeredBy in the
contracts schema test.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

packages/db/test/schema.test.ts

@@ -384,4 +384,25 @@ describe.skipIf(skip)("schema migrations (real PG)", () => {
     expect(up.error).toBeUndefined();
     expect(await tables()).toEqual(EXPECTED_TABLES);
   }, 60_000);
+
+  it("迁移器只内省目标 schema:别处同时建删 schema 不影响(并行测试共用库)", async () => {
+    const migrator = createMigrator(db, { migrationTableSchema: schema });
+    let stop = false;
+    const churn = (async () => {
+      for (let i = 0; !stop && i < 200; i++) {
+        const tmp = `${schema}_churn_${i}`;
+        await sql.raw(`create schema ${tmp}; create table ${tmp}.t (id serial primary key)`).execute(admin);
+        await sql.raw(`drop schema ${tmp} cascade`).execute(admin);
+      }
+    })();
+    try {
+      for (let i = 0; i < 20; i++) {
+        const r = await migrator.migrateToLatest();
+        expect(r.error).toBeUndefined();
+      }
+    } finally {
+      stop = true;
+      await churn;
+    }
+  }, 60_000);
 });