Add CI dogfood workflow and release helpers

[machado144]

Summary

• add a PR/push/manual CI workflow that builds pipekit, runs unit tests, runs binary integration tests, and dogfoods CI-specific behavior
• verify cross-step GitHub env, step outputs, cache-key output propagation, summaries, masking, and exec tee behavior
• add generic CI release helpers: checksum files/verify, artifact assert/manifest, git metadata, and changelog generation
• document the new commands in README, COMMANDS, and EXAMPLES, including a release artifact recipe
• update release workflow and Makefile to run the binary integration suite intentionally

Testing

• go test ./...
• make test-integration
• GitHub Actions CI passed on PR Add CI dogfood workflow and release helpers #3
• inspected the job log and confirmed the new dogfood commands ran, including masked exec output as token=***