ce112bf9ff
- Sent `X-OpenRouter-Cache: false` on bench requests in `bench-cli.ts`: pi-ai opts every OpenRouter request into 1h response caching, so repeated byte-identical runs replayed a cached generation with zeroed usage as "tokens 0, TPS 0.0" successes.
- Added a minimal default `systemPrompt` to bench's request context, matching eval's completion-bridge guard against Codex's HTTP 400 `{"detail":"Instructions are required"}`.
- Checked in `src/prompts/bench.md`, the default bench prompt `bench-cli.ts` already imports (left untracked by 300c1ada30).
- Added both bench changelog entries.