feat(plugins): create conventional-commit-validator hook plugin

[JacobPEvans]

Create Claude Code hook plugin for conventional commit validation.

Repository: jacobPEvans/claude-code-plugins

Implements

• PreToolUse hook on Bash (git commit)
• Validates commit message format
• AI-friendly error messages
• References to commitlint rules

Tasks

• Create plugin structure
• Implement validation logic
• Add comprehensive tests
• Document hook usage

Related

• Depends on: ci(.github): add conventional commit validation (GitHub Action) #27, ci(.github): add conventional commit validation (pre-commit hook) #28 (Commit validation setup)
• Reference: https://github.com/jacobPEvans/claude-code-plugins

Epic

Implements #30