sd_bench grows a directory-entry-scaling section (stat hit/miss and
the loose-object composite at 8/64/256 siblings): FAT resolves every
path component by linear scan, so cost climbing with N convicts
directory scans as the ~360ms residual; flat cost exonerates them.
stage_and_commit brackets the splice with the p_mmap counters and logs
'N mmaps / M KB read' per commit, splitting the residual into pack-read
I/O vs everything else on the next real :sync.
The design record for Typoena — the decisions, specs, and bench write-ups
behind the writing appliance. Start with the ADRs for the
load-bearing choices, or the v0.1 specs for what the
first release actually does.