M14-T01: Build one new engine or engine slice against the extracted substrate

[skel84]

Summary

Use the extracted runtime substrate directly in one new engine or substantial engine slice to prove it reduces copy-paste without degrading correctness.

Scope

• choose one realistic engine or one substantial engine slice
• implement it against the extracted substrate
• keep domain semantics local while reusing the shared runtime modules

Acceptance Criteria

• the implementation uses the extracted substrate rather than local copies
• runtime duplication is materially reduced
• tests and recovery proofs stay green

Canonical Docs

• docs/runtime-extraction-roadmap.md

Blocked By

• M14: Prove the extracted substrate lowers engine-authoring cost #128