refactor(skills): move site-architecture catalogs to references

Keep the decision steps in SKILL.md and move catalogs, examples, and
checklists verbatim to references/ to reduce the context cost of loading the
skill.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

shared/skills/site-architecture/references/page-hierarchy.md

@@ -0,0 +1,53 @@
+# Page Hierarchy Design
+
+## The 3-Click Rule
+
+Users should reach any important page within 3 clicks from the homepage. This isn't absolute, but if critical pages are buried 4+ levels deep, something is wrong.
+
+## Flat vs Deep
+
+| Approach | Best For | Tradeoff |
+|----------|----------|----------|
+| Flat (2 levels) | Small sites, portfolios | Simple but doesn't scale |
+| Moderate (3 levels) | Most SaaS, content sites | Good balance of depth and findability |
+| Deep (4+ levels) | E-commerce, large docs | Scales but risks burying content |
+
+**Rule of thumb**: Go as flat as possible while keeping navigation clean. If a nav dropdown has 20+ items, add a level of hierarchy.
+
+## Hierarchy Levels
+
+| Level | What It Is | Example |
+|-------|-----------|---------|
+| L0 | Homepage | `/` |
+| L1 | Primary sections | `/features`, `/blog`, `/pricing` |
+| L2 | Section pages | `/features/analytics`, `/blog/seo-guide` |
+| L3+ | Detail pages | `/docs/api/authentication` |
+
+## ASCII Tree Format
+
+Use this format for page hierarchies:
+
+```
+Homepage (/)
+├── Features (/features)
+│   ├── Analytics (/features/analytics)
+│   ├── Automation (/features/automation)
+│   └── Integrations (/features/integrations)
+├── Pricing (/pricing)
+├── Blog (/blog)
+│   ├── [Category: SEO] (/blog/category/seo)
+│   └── [Category: CRO] (/blog/category/cro)
+├── Resources (/resources)
+│   ├── Case Studies (/resources/case-studies)
+│   └── Templates (/resources/templates)
+├── Docs (/docs)
+│   ├── Getting Started (/docs/getting-started)
+│   └── API Reference (/docs/api)
+├── About (/about)
+│   └── Careers (/about/careers)
+└── Contact (/contact)
+```
+
+**When to use ASCII vs Mermaid**:
+- ASCII: quick hierarchy drafts, text-only contexts, simple structures
+- Mermaid: visual presentations, complex relationships, showing nav zones or linking patterns