This commit introduces the full downstream runtime implementation needed to ingest, transform, and publish streams.
It preserves the original upstream request boundary by packaging the entire cvmmap-streamer module (build config, public API, protocol and IPC glue, and simulator/tester entrypoints) in one coherent core unit.
Keeping this group isolated enables reviewers to validate runtime behavior and correctness without mixing test evidence or process documentation changes.
Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)
Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>
crosstyan