Lift selected-component properties through abstract finite families #295

AnswersFresh.parallelAll currently repeats reindex, split, binary context and observer transport at the systems layer.

Prove the selected-component transport theorem using Specification and Constructs, with explicit property indices and their transport maps.

Acceptance:

• Assume the property only for the selected component; supply binary-context preservation and structural transport explicitly.
• Instantiate with AnswersFresh, retaining pick, μ and the nonnegativity hypothesis.
• The typed finite-family proof becomes an application of the abstract theorem; primitive freshness proofs remain in RandomSystems.
• Use existing property transport laws rather than a second property foundation.

Depends on: #294, #234. Related: #231.