Arn Spark Feature Extract

- This skill should be used when the user says "feature extract", "arn feature extract", "extract features", "feature backlog", "create backlog", "list features", "what features do we need", "prioritize features", "feature list", "build the backlog", "what should we build", "upload features", "feature tracker", or wants to extract a structured, prioritized feature list with journey steps, validated components, use case context, and UI behavior details from all project artifacts, producing a feature backlog document with a Feature Tracker that bridges into arn-code-feature-spec and optionally uploads features to the issue tracker.