Add compare summary and digest output files (#2)

feat: add compare subcommand for CI regression gating (#1)

fix: use absolute path for --project-root

feat: add --project-root flag to override where commands run from

fix: extract bench.toml to workspace root for stability

feat: add config_path parameter to benchmark workflow

fix: remove extracted bench.toml before compare checkout

fix: use origin/ prefix for remote branch refs

fix: extract bench.toml from compare ref before baseline checkout

fix: handle bench.toml from compare ref for baseline benchmarks

feat: add GitHub Actions workflow for isolated benchmarks

feat: add parallel benchmark execution and timing display

initial commit: generic CLI benchmark harness