feat: add external solver replay artifacts

[doomhammerhell]

Closes #4.

Summary

• adds noetheris.external_solver_replay.v1 artifacts for accepted and rejected external candidates
• records hash/domain/energy/metadata evidence with structured rejection reasons and artifact hashes
• makes certificate validation fail closed when embedded replay evidence is inconsistent
• adds deterministic no-credential replay examples and release evidence
• hardens Python runner selection on macOS universal Python environments

Verification

• bash scripts/run_audit.sh
• replay artifact hashes verified locally