feat(ground-study): add seeded material variation runner

[d-sorgcodexagent]

Summary

• add deterministic VariationPlan-driven variation for base normal restitution and rolling resistance
• preserve immutable per-trial request/SHA provenance through the exact injected flight-to-regional-ground pipeline
• export bounded scalar ensembles with sampled inputs, qualified metrics, and typed-null unavailable rows
• fail closed before execution on unsupported variables, bounds, row caps, or mismatched outcomes

Verification

• 12 focused seeded-variation tests
• 43 focused plus registry tests
• 506 relevant cross-suite tests passed with 6 expected missing-Rust-wheel skips
• Ruff 0.14.10, scoped MyPy, Bandit, campaign manifest, docs/governance, module/structure, and diff gates green

Scope boundary

This advances #4273 and #4267 but does not close them. UI/overlays, persistence, solver/wind integration, compiled parity, downstream propagation, and protected release remain open.

Parent: #4364 exact head f13f090.

[dieterolson]

Consolidated into #4409. Closing to reduce CI/CD runner load.