gentle-ai-bench

## Activation Contract Load when touching `bench/` in gentle-ai, adding or changing a journey, changing a product semantic a journey might pin, or diagnosing a bench failure in CI's Unit Tests job. ## Hard Rules - `go test ./bench` validates corpus declarations only. It does NOT execute journeys. The only driven proof is building the harness and the product binary and running the harness against it; a green `go test ./bench` claims nothing about execution. - Reproduce CI, do not guess invocations: read the Unit Tests step in `.github/workflows/ci.yml` and copy its exact build and `gentle-ai-bench run --binary ...` commands. Use `--only <journey-id>` to drive one journey. - Journey IDs are unique across every `journeys_*.go` file. The collision guard fails loudly naming both files; pick an unused ID by reading the corpus, never reuse a retired one. - Every journey declares `Review:` — `reviewOptedIn` (the runner enables receipt-driven development globally before the first step, uncounted, and fails the journey if the switch does not come on) or `reviewUntouched` (its subject IS the switch, or it has nothing to do with reviews). The declaration is mandatory; `validateCorpus` fails the run without it. Lifecycle journeys must not depend on the product default. Reviews default to ON; `reviewUntouched` does not imply OFF. Journeys requiring OFF must explicitly disable it, while default-mode journeys must assert ON/default with unset sources. - Every `execute` transition must car...