Compiler first witness — execute compiled code with exact meta/native parity

[juv4uk]

Goal

Produce the first end-to-end compiled witness for my-lisp without giving the backend semantic authority.

Pipeline target:

source -> admitted semantics -> IR -> mechanical lowering -> executable form

Required witness

Choose a deliberately narrow but nontrivial program that exercises more than arithmetic alone: lexical binding/closure plus exact arithmetic and at least one canonical control/data operation.

Run the same source through:

• Lisp-owned meta-evaluator;
• current native evaluator;
• compiled execution path.

Require exact observable parity.

Acceptance evidence

• Value parity is exact, including rational identity.
• Relevant errors are parity-checked, not converted to backend-specific behavior.
• Compiler/lowering refuses an unadmitted form.
• No compiler-only primitive is added to the language ontology.

Dependencies

• Compiler authority — make semantic ownership non-negotiable #66
• Compiler oracle corpus — freeze observable semantics before lowering #67
• Compiler IR v0 — provenance-bearing semantics-neutral lowering data #68

Non-goals

• No optimizer in this task.
• No claim that all my-lisp is compiled.