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/investor-pitch-deck/SKILL.md

@@ -42,6 +42,15 @@ For each slide:
 - Investors decide go/no-go on slides 1-5 — front-load evidence
 - Keep to 10-12 slides for a first meeting
 
+## Quality Checks
+
+- [ ] Each slide answers one specific investor question
+- [ ] Slides 1-5 front-load the strongest evidence
+- [ ] Traction slide shows retention and revenue, not just signups
+- [ ] Competition slide does not say "no competitors"
+- [ ] Ask slide specifies use of funds and 18-month milestones
+- [ ] TAM is bottoms-up where possible
+
 ## Example Trigger Phrases
 - "Build a pitch deck structure for [company]"
 - "Help me structure my Series A deck"