Good First Issue: Add GitHub Actions CI workflow for headless automation tests

[ThePecerowski]

Summary

Add a GitHub Actions workflow that runs the UEBPCracker automation test suite headlessly on pull requests and pushes to main.

Background

UEBPCracker already has a complete automation test suite (UEBPCrackerEditorTests module, 28 core + 4 extra modules covered). The headless runner command is documented in CONTRIBUTING.md:

UnrealEditor-Cmd.exe <project> -unattended -nop4 -nosplash -NullRHI
  -ExecCmds="Automation RunTests UEBPCracker;Quit"
  -ReportExportPath=<dir>

Exit code 0 = all pass, 255 = failures.

Challenge

UE 5.8 is a large install (~20–40 GB). Options:

1. Self-hosted runner on a Windows machine with UE 5.8 pre-installed — simplest, recommended for a start
2. Cached UE install in GitHub Actions — complex but works for public repos with large runner storage
3. Docker image with UE 5.8 — requires Epic's Docker setup

Deliverables

• .github/workflows/ci.yml — triggers on PR and push to main
• Runs Development Editor / Win64 build
• Runs headless automation test suite
• Publishes test report as a GitHub Actions artifact
• Adds a build status badge to README

Acceptance Criteria

• CI badge shows on README
• PRs show passing/failing test status before merge

Notes

See CONTRIBUTING.md for the current manual test instructions and headless runner details.