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/press-release/SKILL.md

@@ -64,6 +64,14 @@ ENDS
 ## Journalist Test
 Would a journalist care? Is the headline the full story? Is there a human angle? Is the quote something a human would say? Can the first paragraph stand alone?
 
+## Quality Checks
+
+- [ ] Headline uses active voice and is under 10 words
+- [ ] First paragraph stands alone as the complete story
+- [ ] Quote adds something the facts don't say (not a restatement)
+- [ ] Boilerplate is factual, not promotional
+- [ ] Embargo date and media contact are included
+
 ## Example Trigger Phrases
 - "Write a press release announcing [news]"
 - "Draft a media statement about [event]"