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/sales-battlecard/SKILL.md

@@ -73,6 +73,15 @@ When a prospect mentions [Competitor], say: "[Your positioning in one sentence]"
 We win when: [Scenario — e.g. customer prioritises outcome over price]
 We lose when: [Honest scenario — e.g. primary driver is lowest upfront cost]
 
+## Quality Checks
+
+- [ ] Competitor strengths are listed honestly (not minimised)
+- [ ] Differentiators have proof points (not just claims)
+- [ ] Objection responses are conversational (not scripted-sounding)
+- [ ] Landmine questions are natural and non-confrontational
+- [ ] "When we lose" is included and honest
+- [ ] Battlecard has a review date
+
 ## Example Trigger Phrases
 - "Build a battlecard against [competitor]"
 - "Create a competitive cheat sheet for [competitor]"