v0.12.0: emailType, and info is not something to fix (engine 0.16.0)

• audit_email takes emailType ("transactional" | "marketing"); a receipt marked transactional is no longer told to add an unsubscribe link.
• Engine 0.16.0: resets and progressive enhancement (@media, prefers-color-scheme, partial <style>) are info, so scores rise for most emails.
• audit_email / analyze_email say to fix errors and warnings only; agents used to delete responsive and dark-mode CSS to clear info findings.
• API-key link resolves; links carry utm_source=mcp.