feat: add benchmark reporting command (task 0031)

Add the maintainer-facing `bench:report` command, the offline counterpart
to `bench:run`: it opens the sample store, drains it, aggregates against the
scored suite and bonus definitions, and prints the aggregator's comparison to
stdout. It renders whatever has accumulated, annotating incomplete coverage
rather than blocking on a complete matrix.

`parseReportArgs` is the pure argument seam (`--store`, `--help`, plus a
`--self-review` / `--no-self-review` variant selector). Unlike `bench:run` the
boundary is offline — it reads only the local store, no host or Agent SDK — so
the whole `runReportCommand` is deterministic and unit-tested, not smoke-run.

Move `DEFAULT_STORE_ROOT` to `store.ts` as the single source of truth,
re-exported from `run.ts` for its existing importers.

bench/README.md

@@ -50,8 +50,7 @@ The raw component breakdown is retained on every sample so the data can be re-we
 - `run-loop.ts` — `runCells`, the run loop: it runs one chosen `(arm, task)` cell for a batch of trials (defaulting to five, with a reporting floor of three) by driving `runCell` and the sample store, deciding only how many trials to run and at what trial numbers. Deepening a cell continues numbering past the highest trial it already holds and appends, so a cell's sample size grows across sittings rather than being overwritten. It reimplements no orchestration — provision, run, score, and append stay in `runCell`.
 - `run.ts` — the maintainer-facing run-loop command. `parseRunArgs` is the pure, unit-tested argument seam; `runBenchCommand` is the live boundary that resolves host access, resolves the scored suite against the host's self-review support, selects the task, and drives `runCells`. Invoked via `npm run bench:run` (see below).
 - `aggregate.ts` — the aggregator: the pure seam that renders the accumulated sample store into a readable comparison. `readAllSamples` drains a store into a flat record list; `aggregate` rolls the records up against the task definitions into a `Report` (headline, per-tier and per-token-component breakdowns, and the bonus table); `renderReport` renders that report as stable text. The headline metric, `costEquivalentTokens`, is computed here at render time by weighting the four retained token components by ADR 0014's pricing ratios (fresh input 1×, cache-write 1.25×, cache-read 0.1×, output 5×), so the stored records can be re-weighted without re-running. It reads whatever samples exist and annotates incomplete coverage — cells below the reporting floor (partial) and unsampled cells (missing) — rather than blocking on a complete matrix. A pure function of the records plus the definitions, unit-tested against synthetic append-only sample stores.
-
-The aggregator has no command wrapper yet; a `bench:report` CLI over it is a natural follow-up, in the same shape as `run.ts` is over `run-loop.ts`.
+- `report.ts` — the maintainer-facing reporting command, the counterpart to `run.ts`. `parseReportArgs` is the pure argument seam; `runReportCommand` opens the store, drains it, aggregates against the scored suite and bonus, and prints `renderReport`. Unlike `run.ts` it has no live boundary — it reads only the local store on disk (no credentials, host, or Agent SDK) — so the whole command is deterministic and unit-tested, not smoke-run. Invoked via `npm run bench:report` (see below).
 
 ## Running a cell
 
@@ -67,6 +66,20 @@ Re-running the same cell deepens it — the new trials append rather than overwr
 The command is executed with [`tsx`](https://tsx.is) (a devDependency) so the harness's TypeScript runs directly.
 Like the runner smoke tier it drives the live host and the Claude Agent SDK, so a real run needs a configured login, the `gitea-axi` CLI on `PATH`, the Agent SDK installed (`npm install @anthropic-ai/claude-agent-sdk` — an optional peer, declared but not installed by default), and a Claude subscription.
 
+## Reading the results
+
+The reporting command renders whatever has accumulated in the store into the readable comparison — the cost-equivalent-token headline, coverage annotated against the reporting floor, the per-tier and per-token-component breakdowns, and the bonus table:
+
+```
+npm run bench:report
+```
+
+It reads `bench/results/` by default; pass `--store <dir>` to read a different store, and `--help` for the full flag list.
+Incomplete coverage is annotated rather than hidden, so a half-run matrix still renders (unrun arms show an em dash, not a misleading zero).
+
+Unlike `bench:run` this command is offline — it reads only the local store, never the host — so it needs no login, host, or Agent SDK, and is safe to run at any time.
+The `--self-review` / `--no-self-review` flag only selects the bonus capability catalog (whether the approve/request-changes review pair appears there or in the scored suite); the scored coverage is identical either way, so set it to match the host the samples were run on.
+
 ## Tests
 
 The harness's deterministic seams are unit-tested in this directory, colocated with their source, and run via: