scaffold: M0 skeleton + agent onboarding (build, architecture, progress)

Turn the design into a buildable, dependency-free M0 skeleton plus the
onboarding layer so a new agent can pick up instantly.

Build system:
- CMake + CMakePresets (dev = no deps; server-release = vcpkg) + vcpkg.json
- Skeleton builds with just a C++20 compiler; deps stay off until needed
- .gitattributes (LF), .gitignore, .clang-format

Core (libvoicecat):
- core/include/voicecat.h: full C ABI (the client/server contract), stubbed
- core/proto/voicecat.proto: control-plane wire format, matches docs/protocol.md
- src/{net,crypto,codec,protocol,session,audio,core}: subsystem stubs that
  return VC_ERR_NOT_IMPLEMENTED, each pointing to its design doc
- server/ (voicecat-server) and tools/vccli/ link the core
- tests/: CTest smoke test asserting the C ABI contract (behavior, not just build)
- clients/{apple,windows}: M4 placeholders

Onboarding for agents:
- CLAUDE.md: hub — build/test commands, architecture at a glance, doc map, rules
- AGENTS.md: working method (behavior-driven; clean compile is the floor not the goal)
- PROGRESS.md: living tracker — M0 done, M1 task checklist, "where we left off"

Verified: cmake --preset dev && cmake --build --preset dev && ctest --preset dev → green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/main.cpp

@@ -0,0 +1,68 @@
+/*
+ * voicecat-server entry point (M0 skeleton).
+ *
+ * Goal (docs/deployment.md): one command, zero config, encrypted + listening. Today it
+ * parses a few flags and prints what it would do.
+ */
+#include <cstdio>
+#include <cstring>
+#include <string>
+
+#include "server.h"
+#include "voicecat.h"
+
+namespace {
+
+void print_help(const char* argv0) {
+    std::printf(
+        "voicecat-server %s\n\n"
+        "Usage: %s [options]\n"
+        "  --port <n>          control+media port (default 8384)\n"
+        "  --data-dir <path>   data directory (default ./voicecat-data)\n"
+        "  --name <name>       server name\n"
+        "  --no-guests         disable guest access\n"
+        "  --print-config      print effective config and exit\n"
+        "  --version           print version and exit\n"
+        "  --help              this help\n",
+        vc_version_string(), argv0);
+}
+
+}  // namespace
+
+int main(int argc, char** argv) {
+    voicecat::server::Config cfg;
+    bool print_config_only = false;
+
+    for (int i = 1; i < argc; ++i) {
+        const char* a = argv[i];
+        auto next = [&]() -> const char* { return (i + 1 < argc) ? argv[++i] : ""; };
+        if (std::strcmp(a, "--help") == 0) {
+            print_help(argv[0]);
+            return 0;
+        } else if (std::strcmp(a, "--version") == 0) {
+            std::printf("voicecat-server %s (protocol v%d)\n", vc_version_string(),
+                        VOICECAT_PROTOCOL_VERSION);
+            return 0;
+        } else if (std::strcmp(a, "--port") == 0) {
+            cfg.bind_port = static_cast<uint16_t>(std::atoi(next()));
+        } else if (std::strcmp(a, "--data-dir") == 0) {
+            cfg.data_dir = next();
+        } else if (std::strcmp(a, "--name") == 0) {
+            cfg.server_name = next();
+        } else if (std::strcmp(a, "--no-guests") == 0) {
+            cfg.allow_guests = false;
+        } else if (std::strcmp(a, "--print-config") == 0) {
+            print_config_only = true;
+        } else {
+            std::fprintf(stderr, "unknown option: %s (try --help)\n", a);
+            return 2;
+        }
+    }
+
+    std::printf("[voicecat-server %s] starting\n", vc_version_string());
+    voicecat::server::Server server(cfg);
+    if (print_config_only) {
+        // run() currently just prints config; in M1 split this into a pure config dump.
+    }
+    return server.run();
+}