build-scenario-tests

# Build Scenario Tests Compile one small behavior contract into deterministic, repository-native test code. Understand the host project before choosing a harness, command, fixture, selector, or assertion. ## Operating contract - Treat repository instructions and existing tests as authoritative. - Keep each scenario focused on one behavior and one reason to fail. - Compile into the test stack the repository already uses. Add a dependency only when no suitable harness exists and the user accepts the tradeoff. - Make setup, inputs, actions, and expected results deterministic. - Prefer public behavior over implementation details. Assert what a user or external caller can observe. - Keep the Markdown scenario beside the test or in the repository's established specification directory. Record the mapping in both artifacts. - Never weaken an assertion merely to make a test pass. ## Workflow ### 1. Pass the repository-understanding gate Read the nearest `AGENTS.md` or equivalent instructions, product README, contribution guide, manifests, test configuration, and the smallest relevant product documentation. Use repository search to find the implementation entry point, neighboring tests, fixtures, stable selectors, and validation commands. Trace the relevant action from its public entry point through the state boundary to the observable result. Do not read the entire tree without a reason. Before editing, be able to state: ```text product surface: behavior source: relevant...