chore: remove skeleton build mode and stub #ifdef scaffolding

Drop the M0 no-deps skeleton preset and all VOICECAT_HAS_NET/AUDIO/OPUS/NS
guards that it required. Every subsystem is fully implemented; the stub
#else paths were dead code that added noise to every header and source file.

- CMakePresets.json: remove skeleton configure/build/test entries
- CMakeLists.txt (root/core/tests): remove VOICECAT_USE_VCPKG_DEPS option
  and guards; all targets now build unconditionally
- 17 C++ source files: unwrap HAS_* guards, delete stub #else blocks
- apm_processor.cpp: delete ApmPassthrough no-op class; create() always
  returns RnnoiseProcessor
- 18 test files: remove HAS_* guards and stub int main() skip bodies
- docs/building.md: remove skeleton from preset table and prose

VOICECAT_HAS_LOOPBACK (Windows WASAPI loopback platform gate) unchanged.
29/29 ctest green.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/src/conn_session.cpp

@@ -1,7 +1,5 @@
 #include "conn_session.h"
 
-#ifdef VOICECAT_HAS_NET
-
 #include <algorithm>
 #include <chrono>
 #include <cstdio>
@@ -845,5 +843,3 @@ void ConnSession::send_disconnect_and_close(uint32_t code, const std::string& re
 }
 
 }  // namespace voicecat::server
-
-#endif  // VOICECAT_HAS_NET

server/src/conn_session.h

@@ -11,8 +11,6 @@
 #ifndef VOICECAT_SERVER_CONN_SESSION_H
 #define VOICECAT_SERVER_CONN_SESSION_H
 
-#ifdef VOICECAT_HAS_NET
-
 #include <array>
 #include <atomic>
 #include <chrono>
@@ -184,5 +182,4 @@ class ConnSession : public std::enable_shared_from_this<ConnSession> {
 
 }  // namespace voicecat::server
 
-#endif  // VOICECAT_HAS_NET
 #endif  // VOICECAT_SERVER_CONN_SESSION_H

server/src/db.cpp

@@ -1,7 +1,5 @@
 #include "db.h"
 
-#ifdef VOICECAT_HAS_NET
-
 #include <chrono>
 #include <cstring>
 #include <random>
@@ -612,5 +610,3 @@ int64_t Database::now_unix() const {
 }
 
 }  // namespace voicecat::server
-
-#endif  // VOICECAT_HAS_NET

server/src/db.h

@@ -9,8 +9,6 @@
 #ifndef VOICECAT_SERVER_DB_H
 #define VOICECAT_SERVER_DB_H
 
-#ifdef VOICECAT_HAS_NET
-
 #include <cstdint>
 #include <optional>
 #include <string>
@@ -152,5 +150,4 @@ class Database {
 
 }  // namespace voicecat::server
 
-#endif  // VOICECAT_HAS_NET
 #endif  // VOICECAT_SERVER_DB_H

server/src/identity.cpp

@@ -1,7 +1,5 @@
 #include "identity.h"
 
-#ifdef VOICECAT_HAS_NET
-
 #include <filesystem>
 #include <stdexcept>
 
@@ -35,5 +33,3 @@ bool ServerIdentityManager::init(const std::filesystem::path& data_dir,
 }
 
 }  // namespace voicecat::server
-
-#endif  // VOICECAT_HAS_NET

server/src/identity.h

@@ -7,8 +7,6 @@
 #ifndef VOICECAT_SERVER_IDENTITY_H
 #define VOICECAT_SERVER_IDENTITY_H
 
-#ifdef VOICECAT_HAS_NET
-
 #include <filesystem>
 #include <string>
 
@@ -36,5 +34,4 @@ class ServerIdentityManager {
 
 }  // namespace voicecat::server
 
-#endif  // VOICECAT_HAS_NET
 #endif  // VOICECAT_SERVER_IDENTITY_H

server/src/media_relay.cpp

@@ -1,7 +1,5 @@
 #include "media_relay.h"
 
-#ifdef VOICECAT_HAS_NET
-
 #include <array>
 #include <chrono>
 #include <cstdio>
@@ -179,5 +177,3 @@ void MediaRelay::on_udp_frame(const uint8_t* data, size_t len,
 }
 
 }  // namespace voicecat::server
-
-#endif  // VOICECAT_HAS_NET

server/src/media_relay.h

@@ -16,8 +16,6 @@
 #ifndef VOICECAT_SERVER_MEDIA_RELAY_H
 #define VOICECAT_SERVER_MEDIA_RELAY_H
 
-#ifdef VOICECAT_HAS_NET
-
 #include <memory>
 
 #define ASIO_STANDALONE 1
@@ -71,5 +69,4 @@ class MediaRelay {
 
 }  // namespace voicecat::server
 
-#endif  // VOICECAT_HAS_NET
 #endif  // VOICECAT_SERVER_MEDIA_RELAY_H

server/src/server.cpp

@@ -3,8 +3,6 @@
 #include <cstdio>
 #include <csignal>
 
-#ifdef VOICECAT_HAS_NET
-
 #define ASIO_STANDALONE 1
 #include <asio.hpp>
 #include <asio/signal_set.hpp>
@@ -224,21 +222,3 @@ void Server::stop() {
 }
 
 }  // namespace voicecat::server
-
-#else  // !VOICECAT_HAS_NET
-
-namespace voicecat::server {
-
-int Server::run() {
-    std::fprintf(stderr, "[server] stub: VOICECAT_HAS_NET not defined (build with dev preset)\n");
-    std::printf("  server_name : %s\n", cfg_.server_name.c_str());
-    std::printf("  data_dir    : %s\n", cfg_.data_dir.c_str());
-    std::printf("  bind_port   : %u\n", cfg_.bind_port);
-    return 0;
-}
-
-void Server::stop() {}
-
-}  // namespace voicecat::server
-
-#endif  // VOICECAT_HAS_NET

server/src/session_registry.cpp

@@ -1,7 +1,5 @@
 #include "session_registry.h"
 
-#ifdef VOICECAT_HAS_NET
-
 #include <atomic>
 #include <chrono>
 #include <mutex>
@@ -554,5 +552,3 @@ std::optional<voicecat::v1::AudioConfig> SessionRegistry::channel_audio_config(
 }
 
 }  // namespace voicecat::server
-
-#endif  // VOICECAT_HAS_NET

server/src/session_registry.h

@@ -8,8 +8,6 @@
 #ifndef VOICECAT_SERVER_SESSION_REGISTRY_H
 #define VOICECAT_SERVER_SESSION_REGISTRY_H
 
-#ifdef VOICECAT_HAS_NET
-
 #include <array>
 #include <atomic>
 #include <cstdint>
@@ -223,4 +221,3 @@ class SessionRegistry {
 }  // namespace voicecat::server
 
 #endif  // VOICECAT_SERVER_SESSION_REGISTRY_H
-#endif  // VOICECAT_SERVER_SESSION_REGISTRY_H