INT-OBJECT-01P: Execute owned metaclass subclass checks #271

Scope

Implement metaclass subclasscheck and native type.subclasscheck through owned operations and ordinary callback frames. Preserve callback-before-default validation, tuple/error/short-circuit order, inherited descriptors and truth conversion; validate roots, source errors, limits, collection, cancellation and zero logical teardown. Enable only its adopted corpus stage.

Dependencies and acceptance

Parent: #123 (INT-OBJECT-01). Depends on INT-OBJECT-01O.

Use the existing JavaScript execution machine, explicit classes-source/1 and bytecode 5. Validate against pinned CPython 3.14.7; independently execute adopted source in Node and Chromium with drain and instruction-boundary drivers. Preserve core admission and the eight composed resource observations. Unsupported protocols remain explicit. No dependency, host grant, release, publication or deployment change.

Readiness: Blocked until preceding slice delivers; focused stacked work is allowed.