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/contracts/test/schemas.test.ts

@@ -96,6 +96,7 @@ const OVERRIDES: Record<string, (v: Record<string, unknown>) => Record<string, u
   PathBindingCreate: (v) => ({ ...v, bindingKind: "season", seasonNumber: 1 }),
   OrganizeRequest: (v) => ({ ...v, sourcePaths: undefined }),
   FilesListQuery: (v) => ({ ...v, filter: "video,unidentified" }),
+  EngineRunQuery: (v) => ({ ...v, status: "running,pending", triggeredBy: "user,api_key" }),
   CatalogLookupInput: (v) => v,
   IdentityResolveInput: (v) => v,
   AssetLocationCreate: (v) => v,