v0.2.0 - Add platform fixtures and benchmark runner

Highlights

• Remove public-repository and maintainer placeholders
• Update GitHub Actions to checkout@v7 and setup-python@v7
• Add Shopify Liquid and WooCommerce PHP regression fixtures
• Add reproducible benchmark runner and JSON/Markdown reports
• Expose benchmark execution in CI

Verification

• pytest: 5 passed
• deterministic evals: 7/7 passed
• benchmark fixtures: 7
• expected findings: 10
• detected findings: 10
• missed findings: 0
• unexpected findings: 0

Implemented through #6, #7, and #8.