feat(scripts): Add PHPUnit JUnit XML log parser

- Parses PHPUnit JUnit XML logs for test failures and errors
- Groups errors by type with detailed breakdown
- Archives non-timestamped logs automatically
- Provides concise summary of test results
- Parses both XML (for errors/failures) and stdout (for risky tests/warnings)
- Supports timeout threshold detection from PHPUnit config
- Exit code 1 for failures, 0 for success

This script centralizes log parsing for php-qa-ci workflows and can be used
by phpunit-runner and phpunit-fixer agents.

Usage:
  python3 vendor/lts/php-qa-ci/scripts/parse-junit-logs.py [log-path]

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Joseph Edmonds