scientific(membership): reject contradictory duplicate observation topology in support wire #653

Finding

tepp.membership_observation_support_projection.v1 intentionally preserves duplicate longitudinal observations as a multiset, but canonical Membership state is deterministic for one (MemberId, EventTime): repeating the same observation coordinate must resolve to the same active assignment topology every time.

The current parser validates each row independently, enforces canonical ordering, design/topology consistency, duplicate edge refusal, exact share budgets, and a recomputable wire digest. It does not require two rows with the same (member_ordinal, event_time) to carry identical assignments. A byte-canonical payload can therefore contain two copies of the same local observation coordinate with different valid assignment sets, recompute wire_sha256, and still pass even though no canonical MembershipNetwork can issue that state.

This is distinct from #651: duplicate role/group edges inside one row and same-role share overruns are already rejected. The defect is cross-row determinism for a duplicated observation coordinate.

Required RED

Add a public support-wire fixture with two rows sharing the same member_ordinal and canonical event_time but different individually valid assignment topology. Keep:

• contiguous member/group ordinal spaces;
• a design label consistent with the aggregate reconstructed signals;
• valid exact (0,1] binary64 weights and same-role share budgets;
• canonical row/assignment ordering; and
• a correctly recomputed tepp.membership_observation_support_projection_digest.v1.

MembershipObservationSupportWire::from_json must fail closed. A duplicate coordinate with byte-identical assignments must remain valid so multiplicity is preserved rather than deduplicated.

Minimal causal repair

During wire validation, remember the assignment slice first observed for each canonical (member_ordinal, EventTime) coordinate. A repeated coordinate is valid only when its full ordered assignment vector is identical. Reuse the existing parsed/canonical EventTime and assignment equality; do not add another topology classifier, normalize rows, remove duplicates, or weaken #649/#650 multiplicity semantics.

Boundary

This is reachable-state validation at the Membership serialization boundary. It does not make parsed wire authoritative, add HR/person identity, change estimator arithmetic, or replace release provenance/authentication. #605 remains the canonical owner vehicle and #638/#639 remain downstream until normal protected-main landing.

Refs #605 #638 #639 #649 #650 #651 #652.