feat(skills): add design-motion-principles from kylezantos

Motion/animation design skill with 3-designer lens (Emil Kowalski,
Jakub Krehel, Jhey Tompkins). Two modes: Create and Audit.
Complements frontend-design (broad) with deep motion expertise.

Integration points:
- skills-external/design-motion-principles/ — skill files + references
- link.sh EXTERNAL_SKILLS — symlink to ~/.claude/skills/
- install-plugins.sh step 8c — presence check
- update-all.sh step 7.2 — sync from GitHub
- profiles: design, full, web, web-full — listed as external
- plugin-advisor — decision table, recommended sets, conditional rules
- design-gate — symlink check + non-blocking warning if missing

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

skills-external/design-motion-principles/references/jakub-krehel.md

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+# Jakub Krehel's Animation Principles
+
+Jakub Krehel is a design engineer known for his work at jakub.kr. His approach emphasizes **subtle production polish** — animations that enhance the experience invisibly, designed for real client work where users interact repeatedly.
+
+This file is Jakub's **philosophy and decision frameworks** — the judgment for *how polished* and *how subtle* motion should be. Implementation code lives in `motion-cookbook.md` (cross-referenced below).
+
+---
+
+## Core Philosophy: Invisible Enhancement
+
+> "The best animation is that which goes unnoticed."
+
+His key question for any interaction: **"Is this subtle and polished enough for production?"**
+
+Jakub's work embodies **refinement for production use**. His animations are:
+
+- **Barely noticeable** — If users consciously notice the animation, it's probably too much
+- **Production-ready** — Designed for real client work, not demos
+- **Contextually appropriate** — Adapts to light mode, varied backgrounds, real content
+- **Subtle over flashy** — The goal is to make interfaces feel smooth and responsive, not impressive
+
+**The best compliment**: "This feels really nice" — not "cool animation!"
+
+**The test**: If you remove the animation, do users feel something is missing? Good. If users comment "nice animation!" every time they see it? Too prominent.
+
+---
+
+## When to Apply Jakub's Mindset
+
+- Production applications and client work
+- Professional/enterprise interfaces
+- When users will interact repeatedly (animations must not get tiresome)
+- When accessibility and performance are critical
+- When you need polish without distraction
+
+---
+
+## Signature Techniques (decision context — code in cookbook)
+
+| Technique | When Jakub reaches for it | Cookbook |
+|-----------|---------------------------|----------|
+| Enter recipe (opacity + translateY + blur) | Any element appearing — blur creates a "materializing" feel more physical than fade alone | §1 |
+| Subtler exits | Always — exits don't need the same movement or attention as enters; the user is moving on | §1 |
+| Spring animations (`bounce: 0`) | Production motion — smooth deceleration without overshoot; reserve `bounce > 0` for playful contexts | §2 |
+| Shadows instead of borders | Light mode on varied backgrounds — shadows adapt via transparency where solid borders clash | §3 |
+| oklch gradients | Any gradient — interpolates through perceptually uniform space, avoiding muddy midpoints | §3 |
+| Blur as a signal | Materializing in/out — blur→sharp = entering focus, sharp→blur = losing relevance | §3 |
+| Optical alignment | Buttons with icons, play buttons, asymmetric shapes — trust your eyes over math | §4 |
+| Animated icon swaps (opacity + scale + blur) | Contextual icon changes (copy→check) — instant swaps feel jarring and get missed | §5 |
+| Shared layout via `layoutId` | Smooth FLIP transitions between different components (card→modal) | §6 |
+| Targeted `will-change` | Specific properties about to animate — never global | see `performance.md` |
+
+**Decision rules baked into the techniques:**
+- Exits should always be subtler than enters — smaller movement, same blur.
+- `bounce: 0` is the production default; bounce above zero reads as playful.
+- Borders are fine in dark mode or when you want intentional hard edges.
+
+---
+
+## Common Mistakes (Jakub's Perspective)
+
+- **Making enter and exit animations equally prominent** — Exits should be subtler
+- **Using solid borders when shadows would adapt better** — Especially on varied backgrounds
+- **Forgetting optical alignment** — Buttons with icons, play buttons, asymmetric shapes
+- **Over-animating** — If users notice the animation itself, it's too much
+- **Using the same animation everywhere** — Context should drive timing and easing choices
+- **Ignoring hover state transitions** — Even small transitions (150-200ms) feel more polished than instant changes
+
+---
+
+## Jakub vs. Emil vs. Jhey
+
+| Aspect | Jakub | Emil | Jhey |
+|--------|-------|------|------|
+| **Focus** | Subtle polish | Restraint & speed | Playful experimentation |
+| **Key question** | "Is this subtle enough?" | "Should this animate?" | "What could this become?" |
+| **Signature technique** | Blur + opacity + translateY | Frequency-based decisions | CSS custom properties |
+| **Ideal context** | Production polish | High-frequency tools | Learning & exploration |
+
+**When to use Jakub**: You've decided something should animate (passed Emil's gate) and need to make it production-ready and polished.