feat: Add installation tool, Claude.ai export, and skill standardization (#1)

## Summary

- Add portable installation tool (`install.sh`) for cross-machine setup
- Add Claude.ai export files with proper YAML frontmatter
- Add multi-agent-guide v2.0 with consolidated framework template
- Rename `00-claude-code-setting` → `00-our-settings-audit` (avoid reserved word)
- Add YAML frontmatter to 25+ SKILL.md files for Claude Desktop compatibility

## Commits Included

- `93f604a` feat: Add portable installation tool for cross-machine setup
- `9b84104` feat: Add Claude.ai export for portable skill installation
- `f7ab973` fix: Add YAML frontmatter to Claude.ai export files
- `3fed49a` feat(multi-agent-guide): Add v2.0 with consolidated framework
- `3be26ef` refactor: Rename settings-audit skill and add YAML frontmatter

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

custom-skills/18-seo-gateway-builder/desktop/SKILL.md

@@ -1,3 +1,10 @@
+---
+name: seo-gateway-builder
+description: |
+  Gateway page content builder with templates, schema markup, and local SEO optimization.
+  Triggers: build gateway page, create landing page, local service page, location pages.
+---
+
 # Gateway Page Content Builder
 
 A comprehensive skill for building high-quality, SEO-optimized gateway page content for local services, medical practices, and business locations.