feat(downstream): add cvmmap downstream runtime implementation

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>

src/ipc/help.cpp

@@ -0,0 +1,43 @@
+#include <array>
+#include <string_view>
+
+#include <spdlog/spdlog.h>
+
+#include "cvmmap_streamer/common.h"
+
+namespace cvmmap_streamer {
+
+namespace {
+
+	constexpr std::array<std::string_view, 10> kHelpLines{
+		"Usage:",
+		"  --help, -h\tshow this message",
+		"",
+		"Options:",
+		"  --version\tprint version information",
+		"",
+		"Examples:",
+		"  cvmmap_streamer --help",
+		"  cvmmap_sim --help",
+		"  rtp_receiver_tester --help"};
+
+}
+
+void print_help(std::string_view executable) {
+	spdlog::info("{}", executable);
+	for (const auto &item : kHelpLines) {
+		spdlog::info("{}", item);
+	}
+}
+
+bool has_help_flag(int argc, char **argv) {
+	for (int i = 1; i < argc; ++i) {
+		std::string_view arg{argv[i]};
+		if (arg == "--help" || arg == "-h") {
+			return true;
+		}
+	}
+	return false;
+}
+
+}