Restructure skill numbering: SEO 11-30, GTM 60-69, reserve 19-28 for future skills

Renumber 12 existing skills to new ranges:
- SEO: 11→13, 12→18, 13→16, 14→17, 15→14, 16→15, 17→29, 18→30, 19→12
- GTM: 20→60, 21→61, 22→62

Update cross-references in gateway architect/builder skills, GTM guardian
README, CLAUDE.md (skill tables + directory layout), and AGENTS.md
(domain routing ranges).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

custom-skills/17-seo-schema-generator/code/templates/breadcrumb.json

@@ -0,0 +1,24 @@
+{
+  "@context": "https://schema.org",
+  "@type": "BreadcrumbList",
+  "itemListElement": [
+    {
+      "@type": "ListItem",
+      "position": 1,
+      "name": "{{level_1_name}}",
+      "item": "{{level_1_url}}"
+    },
+    {
+      "@type": "ListItem",
+      "position": 2,
+      "name": "{{level_2_name}}",
+      "item": "{{level_2_url}}"
+    },
+    {
+      "@type": "ListItem",
+      "position": 3,
+      "name": "{{level_3_name}}",
+      "item": "{{level_3_url}}"
+    }
+  ]
+}