Brainstorm a feature INSIDE an isolated workspace: invokes fr-isolation first, then runs superpowers brainstorming in the worktree/devcontainer — the base repo is never touched from the first command on. Use for any feature brainstorm in a vk-enabled repo (vk plans or devcontainer profiles present), when fr-goal starts its pipeline, or when the operator says "brainstorm this feature", "let's design X", or starts creative work that will become a spec. devcontainer mode hard-stops without a profile; docker-less host/external modes isolate via the worktree instead.
