feat(ground): define strict flight transfer contracts

[d-sorgcodexagent]

Summary

Defines the strict, reusable flight-to-ground-request/v1 and flight-to-ground-result/v1 boundary for ground-model epic #4267.

• carries two full signed 3D states bracketing physical sphere/surface contact
• preserves SI units, canonical target frame/origin, complete planar surface/material inputs, calibration, and provenance
• separates carry, bounce-air, skid, roll, surface path, final displacement, and horizontal total distance
• preserves pre/post linear and angular event states and typed unavailable-field evidence
• rejects invalid phase/event/status transitions, fabricated unavailable output, duplicate JSON keys, noncanonical text, unsafe integers, nonfinite values, and raw range/relational violations
• provides deterministic Draft 2020-12 schemas, fail-closed migrations, a shared golden fixture, and an explicit qualified legacy adapter

This PR is intentionally stacked on feat/4197-capability-observer / draft PR #4283. It defines the authority boundary only; #4269 remains responsible for propagating terminal 3D angular velocity and physical contact-bracketing states through Python, TypeScript, Rust, and WASM.

Validation

• 45 focused ground contract/API/schema/migration/parity tests passed
• 180 expanded flight/ground/adapter tests passed
• 4 expected optional Rust-wheel parity tests skipped because the wheel is absent/too old
• Ruff, Black, Python 3.12 mypy, Draft 2020-12 schema meta/runtime validation, structural limits, pre-commit, and diff checks passed
• two independent adversarial reviews found no remaining publication blockers

The Python environment still reports the pre-existing SciPy/NumPy compatibility warning; this change introduces no new warning.

Handoff and specification

SPEC.md, both active campaign handoffs, and the contract specification are updated in the same commit.

Closes #4268