feat: 100 skills milestone — 7 new skills + quality improvements across all 93

New skills added:
- teaching-lesson-plan: structured lesson plans for any subject/audience/setting
- seo-content-brief: complete SEO briefs with intent, competitor gaps, and outline
- media-pitch: story-first journalist pitches with angle development framework
- change-management-plan: stakeholder analysis, comms strategy, adoption metrics
- workshop-facilitation-guide: activity instructions, decision protocols, facilitator moves
- sales-forecasting-model: pipeline model, scenario analysis, assumption log
- tax-planning-checklist: year-end tax planning across income, pension, CGT, reliefs

Quality improvements across all 93 existing skills:
- Standardised description format: "Verb the thing. Use when X. Produces Y."
- Added Required Inputs section to all skills missing it (prompts for missing info)
- Added Quality Checks section to all skills missing it (specific, not generic)
- Fixed broken multiline YAML descriptions
- Removed non-standard frontmatter keys (tool_integration, metadata blocks)

README updated to v6.0.0 with 100-skill count, new skill tables, and article series

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

skills/redundancy-consultation/SKILL.md

@@ -62,6 +62,15 @@ Issued only after genuine consultation. Must include: statutory pay calculated,
 
 WARNING: Take advice from an employment lawyer or qualified HR professional before beginning any redundancy process.
 
+## Quality Checks
+
+- [ ] Number of roles determines consultation type (individual vs collective)
+- [ ] Selection criteria are objective and non-discriminatory
+- [ ] At-risk letter states no decision has been made
+- [ ] Consultation meeting includes genuine exploration of alternatives
+- [ ] Statutory redundancy pay guidance included
+- [ ] Legal advice disclaimer is prominent
+
 ## Example Trigger Phrases
 - "Help me structure a redundancy consultation"
 - "Draft an at-risk letter for [role]"