Public, non-scored qualification sandbox for the canonical cross-domain successor contract.

• Class A is a versioned software-repair environment with source mutation and deterministic build/test verification.
• Class B is a remote resource-allocation environment backed by Val-scoped SQLite/blob state with independently readable post-action state.
• The public surfaces expose outcome goals and ordinary I/O affordances only.
• Hidden benchmark internals, expected choices, and evaluator-only qualification mechanics are not part of the public adapter.
• The capability/source discovery catalogs contain nontrivial alternatives; no fixed benchmark-specific handle is supplied in either public goal.
• The public adapter is compatible with the 2-call and 3-call challenger families.
• No held-out seed is generated and no scored model call is performed by this sandbox.
• This sandbox is candidate qualification infrastructure, not evidence of superhero equivalence, independence, or P_real.

Deterministic internal qualification is implemented in selftest.ts; deployed HTTP-boundary coverage is implemented in http_smoketest.ts.