New spec types: fix bugs and build on top of existing apps

Kiro IDE introduces two new spec types to support developers working on existing codebases. The Design-first workflow lets developers start from a technical architecture rather than requirements, generating a design document first and deriving requirements from it. The Bugfix Spec structures bug fixes into three explicit sections—Current Behavior, Expected Behavior, and Unchanged Behavior—to ensure surgical fixes without regressions. Both workflows integrate with Kiro's property-based testing to verify correctness. These additions complement the existing requirements-first spec flow, giving developers flexibility to match how they actually think about different types of tasks.