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/process-documentation/SKILL.md

@@ -75,6 +75,14 @@ Produces clear, structured process documentation that someone new to a role can
 ### Review
 Next review due: [Date]
 
+## Quality Checks
+
+- [ ] Every step has a named role (not "someone" or "the team")
+- [ ] Edge cases and exceptions table is complete
+- [ ] Prerequisites are listed so someone new can prepare before starting
+- [ ] Escalation path is named (specific people or roles, not just "your manager")
+- [ ] Review date is set
+
 ## Example Trigger Phrases
 - "Document this process: [description]"
 - "Write a process guide for [workflow]"