Work package F: causal support and identifiability

Required data. Complete finite schedules, local channels, references, joint endpoints, complete record laws, and any independent physical causal embedding.

Completed here. Theorem thm:support gives backwards support. Propositions prop:signal-error and prop:physical-causal give conditional stability and geometric containment. Theorems thm:nonidentifiable and thm:statistical give the two possible mechanism verdicts.

Remaining target. Design an actual experiment whose nuisance-enlarged null and alternative record families are separated by one common oriented statistic.

Completion criterion. Either a robust mechanism-specific separation certificate or an explicit observational-equivalence obstruction.