feat: add mcap recorder control and cnats providers

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.

include/cvmmap_streamer/config/runtime_config.hpp

@@ -125,6 +125,7 @@ std::string_view to_string(RtmpTransportType transport);
 std::string_view to_string(EncoderBackendType backend);
 std::string_view to_string(EncoderDeviceType device);
 std::string_view to_string(McapCompression compression);
+std::expected<McapCompression, std::string> parse_mcap_compression(std::string_view raw);
 
 std::expected<RuntimeConfig, std::string> parse_runtime_config(int argc, char **argv);
 std::expected<void, std::string> validate_runtime_config(const RuntimeConfig &config);