**Benchmark YAML exports now quote and escape free-form string fields** (`model`, `model_provider`, `search_engine`, `dataset`, and the evaluator's `model`/`provider`/`endpoint_url`). They were previously interpolated raw, so a value containing a YAML-special character — a colon-space, `#`, quote, or newline — could produce malformed YAML (or inject an unintended key). These fields now go through the existing `yamlEscape()` helper, matching how the settings-snapshot block already serializes strings. Numeric fields and the controlled-format `date_tested`/`ldr_version` are left as-is.
