* test: reproduce accumulated-workspace typing latency through real PTYs
* test: make the bench harness self-checks falsifiable
Review found four assertions that could not fail and one fixture gap:
- `missingPtyArrivalCount`/`missingEchoCount` were hardcoded `0` and
`validateExpectedSeqs` throws before them, so every assertion on them
was vacuous and every report read `0`. The throw is the real guard and
is already covered; drop the vestigial fields.
- An absent status controller returned an all-zero result, which satisfied
its own accepted-equals-generated equality. Assert presence first.
- The byte-pacing control had only an upper bound, so a generator emitting
no stream bytes passed. Add the lower bound.
- `lineageEvery: 1` built zero lineage: no ordinal satisfies
`% 1 === 1`. Offset the interval and cover the densest setting.
- The documented control command never set ORCA_TYPING_BENCH, so it
skipped instead of running.