plan-feature-brainstormlisted

# Plan-feature: brainstorm — STUB Phase 3.2 D-03 WIRED reference implementation. Returns mock decision output for workflow runtime verification. ## Stub behavior This skill stub returns a mock result to simulate phase success transition: ```json { "status": "ok", "output": "<stub for plan-feature-brainstorm>", "decision": "mock-approved" } ``` Phase 3.3+ dogfood: replace stub with actual superpowers brainstorming + ui-ux-pro-max spawn + decision capture.