docs: brand vs product register awareness

## Summary Adds `docs/REGISTER_AWARENESS.md` — a single documentation file that names the brand-vs-product register distinction that emerges after running the skills against both brand surfaces (landing pages, campaign pages) and product surfaces (dashboards, admin tools). Pure documentation addition. No skill content changed, no existing behavior altered. ## Motivation The taste-skill bundle is genuinely useful. After applying the skills across multiple project types, one pattern emerges worth surfacing in the docs: many rules read as **brand-register defaults** when they're applied uniformly to every project. Concretely: - `Inter` banned for premium contexts. In a marketing surface that's the right call; in a product UI (dashboard, admin panel) `Inter` is the common cross-platform default and system fonts are legitimate. - Fluid `clamp()` typography. Brand-shaped. Product UIs are viewed at consistent DPI, and a fluid `h1` that shrinks in a sidebar looks worse than a fixed-rem scale. - Asymmetric / Cinematic Centered / Editorial Split layouts. Brand-shaped. Product UIs lean on predictable grids because consistency is an affordance. - Pseudo-system labels (e.g. `SECTION 04`) are generally right to skip, but a real ops dashboard has legitimate operator labels and small mono metadata. "Skip unless truly necessary" sometimes gets misread as "always skip." ## What this PR contains One new file at `docs/REGISTER_AWARENESS.md` with: - The two registers defined (brand = design IS the product; product = design SERVES the product) - A swap-list of ~14 rules that genuinely diverge between the two - A per-skill register-fit table mapping the current bundle to each register (most skills are brand-default; `minimalist-skill` is closest to product; `output-skill` is register-agnostic) - Two proposed shapes for surfacing register at the skill level — a top-level dial (`REGISTER: brand`) alongside the existing three, OR per-skill frontmatter — without committing to either - Cross-references to [pbakaus/impeccable](https://github.com/pbakaus/impeccable) (Apache 2.0, derives from Anthropic's `frontend-design`) which uses the register split as its primary structuring decision, and to [kylezantos/design-motion-principles](https://github.com/kylezantos/design-motion-principles) for the Frequency Gate that reads cleanly across both registers ## What this PR does NOT contain - No changes to any `skills/*/SKILL.md` files - No new skill added (the doc proposes where a future `product-ui-taste` skill would fit, but doesn't ship one) - No README changes (happy to add a "See also" link if you want it) - No build / config / install-script changes ## Reviewer notes - The doc is meant to give callers and contributors a shared vocabulary, not to force a refactor. The existing bundle keeps working as-is for brand work. - Both proposed register shapes are backward-compatible — default = brand = current behavior. - If you'd rather close this and reuse the framing differently (e.g. integrate into the main README, or split into a smaller note), happy to revise. Thank you for the work on this skill.