PXTA v0.3.0

• pxta diff OLD NEW: compares two audits' findings.json and lists new
  and gone findings, tracker changes per pass (started, stopped,
  more-pages, fewer-pages, other-pages) and banner changes.
• Leaks are matched by rule and parameter (batch line numbers left out),
  sensitive pages by category and search terms by term, never by value, so
  client IDs that change every run don't show up as changes and staging
  compares with production.
• Findings on pages or passes only one audit covered are listed as not
  compared, never as fixed. They count as new when nothing like them
  happened anywhere in the old audit; --new-pages counts every finding on
  a page the old audit never reached as new.
• Exit codes 0 no change, 1 changes, 2 usage or a redacted audit against an
  unredacted one, 3 unreadable or unwritable file. --fail-on exits 1 for a
  new finding at a severity or above, and always for a lost consent pass,
  an audit that visited nothing, or a banner that's gone or can no longer
  be answered.
• Output as text, JSON (--format json, --out), GitHub annotations and a
  Markdown summary built from public fields only.
• GitHub Action: baseline and baseline-fail-on inputs run the diff after
  the check; with baseline-fail-on, the comparison decides the step, so
  problems the baseline already has don't fail it. Outputs diff-exit-code
  and changes; diff.json in the report artifact.