feat: Cross-references tra web-developer e altre skills

Analisi completata:
- Web-developer references rimangono dedicate (tecniche: HTML/CSS/JS)
- Shared references rimangono per UX/design patterns (strategici)

Aggiunti riferimenti incrociati:

1. agency-web-developer:
   - +5 shared references (hero, design, navigation, conversion, layout patterns)
   - Flusso: leggi pattern UX → implementa con technical refs

2. agency-design-system:
   - +3 web-developer refs per handoff tecnico
   - Nota: produce design doc, web-developer implementa codice

3. agency-ux-copy:
   - +design_patterns.md
   - +2 web-developer refs per handoff HTML/CSS
   - Nota: produce copy, web-developer implementa codice

4. agency-seo:
   - +2 web-developer refs per implementazione on-page SEO
   - Nota: produce strategia SEO, web-developer implementa HTML

Flusso chiarito:
- Shared refs = COSA fare (pattern UX/design)
- Web-developer refs = COME codificare (implementazione tecnica)

agency-web-developer/SKILL.md

@@ -320,10 +320,23 @@ $(document).ready(function() {
 
 ## References
 
+### Technical (Web Developer Specific)
 - [html_semantics.md](./references/html_semantics.md) — Semantic HTML best practices
 - [css_layout.md](./references/css_layout.md) — Layout, responsive, Bootstrap
 - [js_interactivity.md](./references/js_interactivity.md) — jQuery + GSAP patterns
 
+### UX/Design Patterns (Shared References)
+**Consultare PRIMA di implementare:**
+- [hero_sections.md](../references/hero_sections.md) — Hero checklist, formula, layouts
+- [design_patterns.md](../references/design_patterns.md) — Card grid, split layout, testimonial, FAQ patterns
+- [navigation_patterns.md](../references/navigation_patterns.md) — Primary nav, mobile nav, IA
+- [conversion_patterns.md](../references/conversion_patterns.md) — CTA hierarchy, forms, friction reducers
+- [layout_systems.md](../references/layout_systems.md) — Grid, spacing, vertical rhythm
+
+**Flusso consigliato:**
+1. Leggi pattern UX da shared references (COSA fare)
+2. Implementa con technical references (COME codificare)
+
 ---
 
 ## Note