doc-bdd

Purpose

Create Behavior-Driven Development (BDD) scenarios — Layer 4 of the SDD flow. A BDD suite translates EARS formal requirements into structured YAML scenarios (Given/When/Then phase lists carried in a ```yaml block, NOT Gherkin @-tags), each carrying an element-level ears: trace list and a spec_trace link forward to the SPEC sections it exercises. (If a runner ever needs .feature files, the YAML is the source of record and a .feature emitter can be authored on demand — no such emitter ships today; the only shipped transcoder is the one-off reverse-direction tools/gherkin_to_bdd_yaml.py used to migrate legacy Gherkin into the YAML form.)

Layer: 4. Upstream: EARS (per the necessary-upstream contract; upstream PRD/BRD lineage is reachable transitively via the @-tag chain). Downstream: ADR → SPEC → TDD → IPLAN → Code.