Web Performance Audit

Produce two deliverables for one URL, always saved in the project's docs/ folder:

docs/<site-slug>-performance/
  report.md          # source of truth, written for coding agents: evidence, code, verification
  report.html        # rendered from report-data.json for human reviewers (tabs, charts, filterable to-do)
  report-data.json   # the numbers and findings both reports are built from
  .gitignore         # ignores raw/
  raw/               # Lighthouse JSON/HTML, traces, heap snapshots, QA screenshots (never committed)

<site-slug> is the bare host, e.g. example-com-performance. If the project has no docs/ folder, create it. Never commit raw/: it is hundreds of MB, and traces from a real browser profile contain cookie IDs and pixel query strings.

Prerequisites

You need Node.js 22.19+ (required by current Lighthouse; on older Node pass --lighthouse 12 to the runner), Google Chrome 144+, the chrome-devtools CLI from the chrome-devtools-mcp package, and ideally the Chrome DevTools MCP server and its upstream skills. Check with chrome-devtools --version. If anything is missing, follow setup once, then continue.