Add multi-engine run dossier capture

[xtraid]

Summary

• add closed v2 case and dossier contracts with fixed named engine, verification, presentation, timing, and artifact fields
• capture Boolean Z3, one native reduction, reference, optimized, and Wang Z3 exactly once, with hash-coherent trace v3 bundles and existing independent checkers
• preserve v1 behavior behind the single public CLI while installing a self-contained v2 directory atomically

Test plan

• make check
• renderer: uv run --locked pytest -q (283 passed)
• make run-dossier-smoke
• focused SAT, UNSAT, mismatch, tamper, cleanup, and atomic replace coverage

Timings are run-specific observations, not benchmark claims. V2 narrative assets and PDF composition remain downstream work.