chore: release v4.0.0 - sync 550+ skills and restructure docs

skills/startup-metrics-framework/SKILL.md

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+---
+name: startup-metrics-framework
+description: This skill should be used when the user asks about "key startup
+  metrics", "SaaS metrics", "CAC and LTV", "unit economics", "burn multiple",
+  "rule of 40", "marketplace metrics", or requests guidance on tracking and
+  optimizing business performance metrics.
+metadata:
+  version: 1.0.0
+---
+
+# Startup Metrics Framework
+
+Comprehensive guide to tracking, calculating, and optimizing key performance metrics for different startup business models from seed through Series A.
+
+## Use this skill when
+
+- Working on startup metrics framework tasks or workflows
+- Needing guidance, best practices, or checklists for startup metrics framework
+
+## Do not use this skill when
+
+- The task is unrelated to startup metrics framework
+- You need a different domain or tool outside this scope
+
+## Instructions
+
+- Clarify goals, constraints, and required inputs.
+- Apply relevant best practices and validate outcomes.
+- Provide actionable steps and verification.
+- If detailed examples are required, open `resources/implementation-playbook.md`.
+
+## Resources
+
+- `resources/implementation-playbook.md` for detailed patterns and examples.