[Feature] Add a planning-phase skill for design direction before implementation

[Caperious]

What problem does this solve?

There's no impeccable skill I can reference during the planning/brainstorming phase. All
existing skills kick in at implementation time — but by then, the spec and plan are
already written without any design thinking.

I use superpowers' brainstorming and writing-plans skills to produce specs and plans
before building. I'd love to invoke an impeccable skill during that phase to establish
creative direction, but nothing exists for that. So design context only enters the picture
when I run something like /frontend-design to write code — too late to shape the
decisions that matter most.

Proposed solution

A skill like /design-brief or /creative-direction that helps establish aesthetic
direction, constraints, and design strategy — without producing code. Something I can
invoke during planning to get a design-informed brief that guides the rest of the
workflow.

It would read .impeccable.md (or prompt /teach-impeccable if missing), then help shape
decisions like layout approach, interaction patterns, visual hierarchy, and tone — before
any implementation skill runs.

Provider(s) this applies to

• All providers

Alternatives considered

• Running /frontend-design during planning — but it's built to produce code, not inform
  specs.
• Running /teach-impeccable before planning — saves the file, but no existing skill reads
  it during spec/plan creation.
• Adding design context to CLAUDE.md manually — works as ambient context but isn't a
  structured part of the design workflow.