kaas-test-harness

Shared test helpers — the only place in the workspace where a decoded-record representation is allowed to live.

Still essentially a stub, populated as integration tests need it. Its charter is narrow and deliberate: test fixtures (including the byte-opacity fixtures) and the recordbatch helper for constructing RecordBatches in tests. Production crates must never grow a decoded-record type — when a test needs one, it lives here, where the tripwire counters can't be quietly bypassed (wire protocol).