Initial commit: Superpowers plugin v1.0.0

Core skills library as Claude Code plugin:
- Testing skills: TDD, async testing, anti-patterns
- Debugging skills: Systematic debugging, root cause tracing
- Collaboration skills: Brainstorming, planning, code review
- Meta skills: Creating and testing skills

Features:
- SessionStart hook for context injection
- Skills-search tool for discovery
- Commands: /brainstorm, /write-plan, /execute-plan
- Data directory at ~/.superpowers/

skills/INDEX.md

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+# Claude Superpowers
+
+Your skills library of proven techniques, patterns, and tools.
+
+## First Time Here?
+
+**Read this first:** skills/getting-started - Introduction to the skills library and how to use it
+
+## Quick Start
+
+**Starting a task?** Check the relevant category below.
+**Encountering a problem?** Search with: `${CLAUDE_PLUGIN_ROOT}/skills/getting-started/skills-search keyword`
+**Not sure?** Ask your human partner: "Do I have a skill for X?"
+
+## Categories
+
+- skills/testing - Writing reliable, maintainable tests (TDD, async testing, anti-patterns)
+- skills/debugging - Finding and fixing bugs systematically (root cause tracing, verification)
+- skills/collaboration - Working with other agents and developers (brainstorming, planning, code review)
+- skills/meta - Using, creating, and testing skills
+
+## Navigation
+
+Each category INDEX shows available skills with descriptions. Load the category relevant to your current work.
+
+## Creating New Skills
+
+See skills/meta/creating-skills for guidelines on documenting new techniques.