feat: add framework-neutral execution contract v1

[ndrorchestration]

Summary

Adds the first ACP-native implementation of the framework-neutral cross-runtime execution/trace contract defined in the September architecture work.

Implemented

• versioned agent-control-plane.execution.v1 schema identity;
• typed execution, trace/span, component/runtime/adapter, artifact, and event records;
• canonical UTC Z serialization plus monotonic event ordering value;
• deterministic to_dict() serialization and validated ExecutionEvent.from_dict() round-trip;
• fail-closed validation for required identity, schema version, span self-parenting, malformed SHA-256, nested contract types, monotonic values, and UTC timestamps;
• explicit mapping from legacy ProvenanceEvent into the new contract when the caller supplies missing execution/trace/component context;
• fail-closed provenance/contract run-ID mismatch;
• exact unspecified status when legacy provenance has no state;
• design, implementation plan, README, and kernel-spec evidence-boundary documentation.

Compatibility

• Existing Task, ControlPlane, budgets, policy behavior, and root public imports are unchanged.
• agent-control-plane.provenance.v1 remains unchanged and process-local.
• No external runtime/framework adapter is added in this PR.
• No external dependency is added.

TDD / verification evidence

Implementation used explicit RED → GREEN cycles. Representative RED evidence includes missing contract module/types, missing mapper, missing round-trip constructor, and review-discovered nested-type validation failures. The review regression at 00538b772356f0b4c2884a281015696696e2db13 produced exactly 6 intended failures with 58 other tests passing.

Final exact implementation head: 07a09698ca66e8837d04e6ec05b4de3448eced04.

Push workflow run 34909375428 completed SUCCESS on that exact head across Python 3.10, 3.11, 3.12, 3.13, and 3.14.

Evidence ceiling

This PR can support the claim that ACP implements and tests a versioned framework-neutral execution/trace contract for its native representation under the tested conditions.

It does not establish:

• general cross-runtime portability;
• two-runtime conformance without schema fork;
• DGAF authorization or governance efficacy;
• PDMAL scientific validity or efficacy;
• durable/tamper-evident provenance or cryptographic attestation;
• distributed reliability or production readiness;
• superiority to existing orchestration standards/frameworks.

Cross-runtime portability remains NOT ESTABLISHED.

Base lineage: dbab7c1afafec524ce7c18157de2089cafe79c87.