Portable v3 CellBuffer operation traces

[PerchAnton]

Would small, portable CellBuffer operation traces be useful for regression reports?

I built an external adapter against current v3. Three scenarios exercise native Put/Resize/Fill/Get calls: grapheme widths and remainders, dirty-state invalidation after resize, and out-of-bounds writes. All 13 steps, adapter race tests and go vet pass locally.

I maintain the experimental interaction-check runner. It adds an optional JSON replay format alongside native Go tests. This is buffer-level coverage, not terminal emulation or input decoding, and is separate from the stdin-replay question in #605.