Enforce BDD feature and fixture naming consistency

[leynos]

Problem

The 2026-06-05 code-base audit found that BDD feature files, scenario modules, and fixture modules do not have an enforced naming relationship. The current convention is discoverable by inspection, but drift is easy as the suite grows.

Suggested fix

Codify the naming convention between tests/features/*.feature, tests/scenarios/*_scenarios.rs, and tests/fixtures/*.rs. A lightweight manifest test or registration check should fail when a feature lacks the expected scenario or fixture wiring.

Context

Related draft plan: #534

This is intentionally tracked outside the current ExecPlan because the plan only touches BDD wiring where it is directly needed for the requested refactors.

[coderabbitai]

🔗 Related PRs

#527 - Add wireframe-verification crate with placeholder Stateright model (15.1.2) [merged]
leynos/mdtablefix#276 - Cli matrix testing [merged]
leynos/tei-rapporteur#79 - Use named validation BDD scenarios (#34) [merged]
leynos/rstest-bdd#493 - Implement first-party harness-led attribute defaults (9.7.2) [merged]
leynos/rstest-bdd#496 - Surface GPUI scenario names on panic (10.1.4) [merged]

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