Separate semantic copy identity from optional encoded-byte coverage #1170

Deferred from the closing review of #1116 for declarative sharding (Pro #980). The owner explicitly scoped this root cause out of the closing implementation batch.

Current assessment: Decoded full body plus metadata is the semantic contract; harmless shared-structure re-encoding need not be byte-identical. Optional encoding coverage is separate.

Owning path: unitTests/replication/residencyReplicaWire.test.mjs. Review lines move as the companion branches integrate main; use the linked PR's current source.

Follow-up: Implement and verify the scoped documentation or test improvement without expanding the current runtime contract.

This issue does not reopen #980's approved primary-key-only scope, complete-history requirement, or ban on write serialization. It does not block the current drafts. No release or backport is committed; milestone is intentionally unset. Found through source review and synthetic tests; there is no customer-specific incident evidence.

Triage: P3; effort Low; type Task. Low-priority follow-up: no demonstrated correctness failure or new release requirement. This is deliberately below the parent reliability priority.

Finding IDs: 94eb3020d6da.

Review-Deferral: 2fedf27cb146a8c6 severity=nit category=test-coverage

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Additional review identifiers for this root cause

Review-Deferral: 5c857798ee832383 severity=minor category=test-coverage