brainstorm

Runs a structured design conversation — clarifies intent, proposes 2-3 approaches with trade-offs, iterates the design — and writes a user-approved engineering spec to docs/specs/ that /optimus:tdd auto-detects. No implementation happens until the spec is approved. With the scaffold argument, creates docs/product/ steering skeletons instead (never overwrites, authors no content). Run /optimus:init first.