One-shot second-opinion diff review by a different-model seat, advisory only

Comparison

• vs /roundtable — the round table convenes every seat for deliberation with a chair-ruled promotion flow; cross-review is one seat, one pass, on a concrete diff. Use the table for design questions, cross-review for "does another model see a problem in this change?"
• vs /deep-review — deep-review is a multi-pass review by the same model family driving your session; cross-review's value is precisely that the reviewer is a DIFFERENT model with different blind spots.
• vs CI review bots — cross-review never gates anything; it is advisory input to a human, recorded on the board and in the ledger.