feat(ground): add passive impact and repeated bounce

[d-sorgcodexagent]

Summary

• add a typed passive restitution/Coulomb sphere-plane impact solver with full sphere-spin coupling and moving-surface energy accounting
• interpolate exact first contact and deterministic repeated ballistic recontact under versioned standard gravity
• expose a validated impact/bounce prefix with exact events, trajectory samples, airborne-segment distance evidence, bounded cancellation/termination, and one terminal SKID handoff
• preserve absolute public timestamps while measuring max_time_s from interpolated first contact and counting FIRST_CONTACT against max_events
• pin the scientific contract, shared golden fixture, API surface, campaign authority, SPEC, and all durable handoffs

Tracks #4270 under ground-model epic #4267.

Exact stack evidence

• current PR head: 920c46dee688815691e251777142126bf1489b1a
• immutable implementation evidence: 63a6f4bec63c58d28bceed2e8cf348a618c8e366
• exact base: 4972e55e0bb6e5b6bf7da0f899eed5d4f54e7d9d (feat/4269-flight-ground-transfer, PR feat(flight-ground): qualify physical transfer state #4288)

No existing PR base was changed; this is the next normal child in the ground stack.

Verification at immutable implementation evidence

• CPython 3.10.20 full ground suite: 82/82
• CPython 3.11.9 full ground suite: 82/82
• independent Python 3.13 full ground suite: 82/82
• pinned mypy 1.13: 17 ground production modules, no issues
• pinned Ruff 0.14.10 check/format: pass
• campaign manifest validator: pass
• campaign manifest tests: 8/8
• documentation governance: pass
• module/function/signature budgets: pass
• shared golden SHA-256: 5831a8f8bf0fe18edf76c985503fdfe784df8e0eed89f85deb9c27085fb9f059
• git diff --check: pass

Current-head CI correction

Hosted quality-gate run 31350134551 on the previous docs head exposed four actionable pinned-MyPy findings. Commit 920c46dee688815691e251777142126bf1489b1a binds the lazy serializer result to its declared mapping type and narrows the guarded output-grid time to a local float; physics, schema, numerical order, outputs, scope, and base are unchanged.

Current-head local revalidation:

• CPython 3.10.20 full ground suite: 82/82
• CPython 3.11.9 full ground suite: 82/82
• pinned MyPy 1.13: exact failing 2-file slice and all 17 ground modules, no issues
• Ruff check/format and git diff --check: pass

Deliberate boundary

This PR is not a final ground simulation. Issue #4271 retains skid, roll, rest, total distance, regional surfaces, and composition into GroundSimulationResult. The v1 bounce law deliberately does not consume firmness, grass, compressibility, moisture, or rolling resistance. PyQt/React UI, TypeScript/Rust/PyO3/WASM physics, and downstream UpstreamDrift integration remain separately tracked.

Release boundary

This is draft-PR evidence only. Protected CI, required review, parent integration, and ordinary release remain open; issue #4270 must not be closed before those gates pass.

[dieterolson]

Consolidated into #4409. Closing to eliminate CI runner load.