Lambda calls in sx_call now go through the CEK machine instead of
returning a Thunk for the tree-walker trampoline. This lets perform/
IO suspension work everywhere — including hyperscript wait/bounce.
Key changes:
- sx_runtime: Lambda case calls _cek_eval_lambda_ref (forward ref)
- sx_vm: initializes ref with cek_step_loop + stub VM for suspension
- sx_apply_cek: VmSuspended → __vm_suspended marker dict (not exception)
- continue_with_call callable path: handles __vm_suspended with
vm-resume-frame, matching the existing JIT Lambda pattern
- sx_render: let VmSuspended propagate through try_catch
- Remove invalid io-contract test (perform now suspends, not errors)
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>