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/patient-communication/SKILL.md

@@ -83,6 +83,15 @@ Yours sincerely, [Name, Title, Department]
 - Use "you" and "we" throughout
 - Numbers as digits: "2 tablets" not "two tablets"
 
+## Quality Checks
+
+- [ ] Written at or below Grade 8 reading level (short words, short sentences)
+- [ ] Active voice used throughout ("We will contact you" not "You will be contacted")
+- [ ] Results letter states the result in the first sentence
+- [ ] Next steps are specific and include timeframes
+- [ ] No Latin or acronyms without explanation
+- [ ] Disclaimer that clinical review is required before sending
+
 ## Example Trigger Phrases
 - "Write a patient letter about [topic]"
 - "Create a patient information leaflet for [procedure]"