feat(skills): bulk-add root SKILL.md to 61 skills (native Agent Skills loadability)

Run the additive migration pass from SKILL-MIGRATION-GUIDE: generate a root SKILL.md
for every skill that lacked one, copied from its desktop/SKILL.md (or code/SKILL.md),
with name set to the directory name and description + body preserved verbatim.

- scripts/migrate_skill_root.py: the reusable, non-destructive migrator (dry-run default).
- 61 new root SKILL.md (desktop source for most; code/SKILL.md for 61/62/92).
- Untouched: 16/17/95 (already had root); desktop/ and code/ packaging left intact.
- All 64 root SKILL.md validate: frontmatter <=1024, kebab name, description present.

Still MANUAL (no SKILL.md source — commands/README only), need hand-authored root SKILL.md:
81-mac-optimizer, 90-reference-curator, 91-multi-agent-guide, 94-dintel-bootstrap.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

custom-skills/14-seo-core-web-vitals/SKILL.md

@@ -0,0 +1,117 @@
+---
+name: 14-seo-core-web-vitals
+description: |
+  Core Web Vitals analyzer for LCP, FID, CLS, and INP optimization recommendations.
+  Triggers: Core Web Vitals, page speed, LCP optimization, CLS fix, INP analysis.
+---
+
+# SEO Core Web Vitals
+
+## Purpose
+
+Analyze Core Web Vitals performance metrics and provide optimization recommendations.
+
+## Core Capabilities
+
+1. **LCP** - Largest Contentful Paint measurement
+2. **FID/INP** - Interactivity metrics
+3. **CLS** - Cumulative Layout Shift
+4. **Recommendations** - Optimization guidance
+
+## Metrics Thresholds
+
+| Metric | Good | Needs Work | Poor |
+|--------|------|------------|------|
+| LCP | ≤2.5s | 2.5-4s | >4s |
+| FID | ≤100ms | 100-300ms | >300ms |
+| CLS | ≤0.1 | 0.1-0.25 | >0.25 |
+| INP | ≤200ms | 200-500ms | >500ms |
+
+## Data Sources
+
+### Option 1: PageSpeed Insights (Recommended)
+Use external tool and input results:
+- Visit: https://pagespeed.web.dev/
+- Enter URL, run test
+- Provide scores to skill
+
+### Option 2: Research Best Practices
+```
+mcp__perplexity__search: "Core Web Vitals optimization [specific issue]"
+```
+
+## Workflow
+
+1. Request PageSpeed Insights data from user
+2. Analyze provided metrics
+3. Identify failing metrics
+4. Research optimization strategies
+5. Provide prioritized recommendations
+
+## Common LCP Issues
+
+| Cause | Fix |
+|-------|-----|
+| Slow server response | Improve TTFB, use CDN |
+| Render-blocking resources | Defer non-critical CSS/JS |
+| Slow resource load | Preload LCP image |
+| Client-side rendering | Use SSR/SSG |
+
+## Common CLS Issues
+
+| Cause | Fix |
+|-------|-----|
+| Images without dimensions | Add width/height attributes |
+| Ads/embeds without space | Reserve space with CSS |
+| Web fonts causing FOIT/FOUT | Use font-display: swap |
+| Dynamic content injection | Reserve space, use transforms |
+
+## Common INP Issues
+
+| Cause | Fix |
+|-------|-----|
+| Long JavaScript tasks | Break up tasks, use web workers |
+| Large DOM size | Reduce DOM nodes |
+| Heavy event handlers | Debounce, optimize listeners |
+| Third-party scripts | Defer, lazy load |
+
+## Output Format
+
+```markdown
+## Core Web Vitals: [URL]
+
+### Scores
+| Metric | Mobile | Desktop | Status |
+|--------|--------|---------|--------|
+| LCP | Xs | Xs | Good/Poor |
+| FID | Xms | Xms | Good/Poor |
+| CLS | X.XX | X.XX | Good/Poor |
+| INP | Xms | Xms | Good/Poor |
+
+### Overall Score
+- Mobile: X/100
+- Desktop: X/100
+
+### Priority Fixes
+1. [Highest impact recommendation]
+2. [Second priority]
+
+### Detailed Recommendations
+[Per-metric optimization steps]
+```
+
+## Limitations
+
+- Requires external PageSpeed Insights data
+- Lab data may differ from field data
+- Some fixes require developer implementation
+- Third-party scripts may be difficult to optimize
+
+## Notion Output (Required)
+
+All audit reports MUST be saved to OurDigital SEO Audit Log:
+- **Database ID**: `2c8581e5-8a1e-8035-880b-e38cefc2f3ef`
+- **Properties**: Issue (title), Site (url), Category, Priority, Found Date, Audit ID
+- **Language**: Korean with English technical terms
+- **Audit ID Format**: [TYPE]-YYYYMMDD-NNN
+