fix(skills): add Anti-Patterns sections, fix descriptions, quality checks, and required inputs

- Add Anti-Patterns section (3-5 binary checkboxes) to all modified skills
- Fix Quality Checks to use binary checkbox format where needed
- Rewrite descriptions to verb-when-produces format where needed
- Add Required Inputs sections to skills missing them
- Fix email-triage frontmatter YAML quoting

https://claude.ai/code/session_01MuGKn3a3Gbqoe8uM5Lmuqt

skills/seo-content-brief/SKILL.md

@@ -124,3 +124,11 @@ Each heading is the exact H2/H3 to use (these are what Google reads):
 - "Create a content brief for [topic]"
 - "What should I include in a blog post about [keyword]?"
 - "Build a content strategy brief for [topic]"
+
+## Anti-Patterns
+
+- [ ] Do not write an outline that answers a different question than the actual search intent — the brief must match what the searcher wants, not what the brand wants to say
+- [ ] Do not set keyword density targets so high that they produce unnatural writing — 3–5 natural mentions is guidance, not a quota
+- [ ] Do not skip the competitor gap analysis — without it, the brief produces content that duplicates what already ranks
+- [ ] Do not leave the FAQ section without real "People Also Ask" questions — fabricated questions miss search volume opportunities
+- [ ] Do not write a title tag longer than 60 characters — it will be truncated in search results and undermine ranking