feat: v0.2.0 — release builds, readiness, skip steps, output improvements

[codesoda]

Summary

• Add GitHub Actions release workflow: builds mac arm64 binary on v* tag push, creates draft GitHub Release
• Installer (curl|sh) downloads pre-built binary from releases; local clone builds from source
• Support multiple readiness_urls and configurable readiness_timeout_secs per command
• Add skip = true on test steps to skip execution (counts as passed) — enables checkpointing workflows
• New EXIT_SETUP_ERROR (code 6) for setup command failures (was incorrectly reported as config error)
• Print stdout/stderr tail inline when setup commands fail
• Include artifact directory paths in bootstrap message sent to agent
• Show version banner, relative paths, per-test run info in CLI output
• Update example configs with consistent agent_args
• Bump version to 0.2.0

Test plan

• Run bugatti test with skip = true on steps and verify they show as SKIP and count as passed
• Run with a failing setup command and verify stdout/stderr is printed inline with exit code 6
• Verify readiness_urls (array) and readiness_timeout_secs work in config
• Run ./install.sh from a clone and verify it builds and installs
• Tag a release and verify the GitHub Actions workflow builds and creates a draft release