Register an MCAP recorder service on the streamer control subjects, reuse the shared recording request and status model, and expose the zed recording preview/conversion helper.
This also replaces the temporary cnats boolean with the explicit CVMMAP_CNATS_PROVIDER modes and documents the supported system and workspace build paths.
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