Retain the agent's final report on the benchmark result record for read
tasks, so a failed read is diagnosable directly from the stored record
instead of only carrying an opaque `incorrect` tag. The runner resolves
the scoring spec once and records `run.finalReport` when the spec is a
read; mutation records omit the field entirely. The sample store needs no
change — it serializes whatever record it is handed.
This is the prerequisite for confirming the read-open-issue-count failure
from real report text before the state-aware count-line change (task 0033).
Lay the foundation the benchmark harness reads and writes: a bench/
directory (excluded from the published npm package), the immutable
result-record shape, and an append-only per-cell sample store.
- bench/result.ts: the ResultRecord shape — four token components,
turns, duration, imputed cost, tagged pass/fail outcome, and the
arm/task/tier/trial/timestamp tags. Arm and Tier are typed unions.
- bench/store.ts: append-only sample store, one JSONL file per cell at
<root>/<arm>/<taskId>.jsonl; deepening a cell only ever adds samples.
- bench/README.md: harness working docs and benchmark vocabulary, kept
out of the tool's domain glossary per the spec.
- Dedicated bench test tier (vitest.bench.config.ts, npm run test:bench)
kept out of the fast tier; tsconfig typechecks bench.
- Packaging tier asserts bench/ never ships in the tarball.
