- Remove unused `engine` parameter from `_resolve_engine()` signature and call sites
- Warn on unknown engine in `_has_api_key()` instead of silently returning True
- Warn when budget value from profile is not in BUDGET_ENGINE_MAP
- Validate `platforms` type in `_resolve_platforms()`, wrap non-list values
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>