Multi-agent ideation against a free-form prompt. Wraps `jutsu swarm brainstorm "<prompt>"` to run claude / codex / antigravity in parallel with three different angles (claude=long-horizon framing, codex=code-pattern grounding, antigravity=cross-domain analogy), synthesizes into a ranked list of approaches with tradeoffs. Use when the user says "brainstorm", "ideas for", "how should we approach", "options for", or invokes /brainstorm. Designed to feed into `decide` (for ADR capture of the picked option) or `refactor-plan` (for execution of the picked option).
