Feat/ci list failed tests

[PUSHPAK-JAISWAL]

What & why

When tests fail during a GitHub Actions run, identifying which tests failed and locating their interactive trace files currently requires downloading and unpacking artifact zip archives.

This PR adds automatic job summary reporting:

• Auto-detects GitHub Actions execution via CiEnvironmentDetector.isGitHubActions().
• When tracing.enabled: true is set and tests fail, appends a GitHub Flavored Markdown table (Test, Error, Trace) directly to $GITHUB_STEP_SUMMARY.
• Each table row highlights the failed test ID, the sanitized error message, and the relative path to the trace file (e.g. target/traces/ClassName/testMethod-trace.html or build/traces/... for Gradle).
• Fully no-ops outside GitHub Actions, when tracing.enabled is false, or when no tests fail.
• Integrated into both TestNG (SuiteExecutionListener) and JUnit 5 (SeleniumBootLauncherListener).

Closes #137
Related: #129, #130

Type of change

• Bug fix
• New feature (opt-in, aligned with the framework philosophy)
• Documentation
• Internal refactor / test coverage

Checklist

• All existing tests pass (mvn clean verify)
• New behaviour is covered by unit tests
• No new external dependencies introduced without prior discussion
• Code follows existing conventions (no new frameworks, minimal abstraction)
• No breaking changes to @SeleniumBootApi public APIs (or a major version bump is justified below)
• Docs updated if user-facing behaviour changed (docs-site/)

Notes for reviewers

• Markdown table escaping: Newlines (\r\n, \n) in error messages are normalized to spaces and pipe characters (|) are escaped (\|) to prevent broken table row formatting in GitHub Actions.
• Cross-platform path resolution: Trace paths are normalized to forward slashes (/) across Windows and Unix runners, resolving against ReportPaths.baseDir() (target or build).
• File appending: Uses StandardCharsets.UTF_8 in append mode (FileWriter(file, true)) so any existing step summary output from earlier steps in the workflow is preserved.
• Testability: An override property (-Dseleniumboot.github.step.summary) is supported so the summary export logic can be tested in CI/CD and unit tests without needing process-level environment variable mutation.
• Docs:
  • Added step summary documentation and example to docs-site/docs/ci/github-actions.md.
  • Added the Trace Viewer guide in docs-site/docs/guides/trace-viewer.md and registered it in docs-site/sidebars.js (resolving docs(guide): document the Trace Viewer #129).
  • Updated CHANGELOG.md and docs-site/docs/changelog.md under [Unreleased].