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/

commands/brainstorm.md

@@ -0,0 +1,5 @@
+---
+description: Interactive design refinement using Socratic method
+---
+
+Read and follow: ${CLAUDE_PLUGIN_ROOT}/skills/collaboration/brainstorming/SKILL.md