#4532 GCP codegen: StateData inferred from StateSchema may hit TS2589 now that nested state objects are .partial()

Follow-up from swamp-club #2487 (PR 673). The AWS generator now emits StateData as Record<string, unknown> because inferring it from the all-optional nested StateSchema exceeded TypeScript instantiation depth (TS2589) on QuickSight. The GCP generator (codegen/gcp/extensionModelGenerator.ts, the StateData line) still emits z.infer of StateSchema. GCP StateSchemas are depth-capped at 5 and type-check today, but a deeper discovery schema could fail deno check after a regen. StateData is only a cast target there too, so the same Record<string, unknown> change applies. Raised as a low finding by both verification reviewers.