nx_bench_companion_tsv.nx

nx_bench_companion_tsv.nx -- emit NxBenchReport as TSV row to a caller-provided byte buffer. Sibling to [[nx_bench_companion]]. Substrate-honest persistence: the bench primitive captures counters; this primitive serializes them so they survive process exit + cross-session comparison becomes a `sort -t$'\t' -k4 -n` away. Format: tab-separated, label first, then 19 counter columns. Header row emitted by nx_bc_emit_tsv_header(). Data row by nx_bc_emit_tsv_row(). Both return byte-length written (>= 0) or NEGATIVE on buffer overflow. Per CARDINAL [[feedback-no-strawman-perf-comparisons]]: persisting the counters to disk lets future Nishi-vs-llama.cpp comparison rigs read paired rows + emit honest deltas without re-running every measurement.