Add Windows cross-platform support alongside Linux

Replace POSIX-specific socket and process APIs with portable
abstractions so the project builds on both Windows and Linux.

- Add include/network/net_platform.hpp: Winsock2/POSIX socket
  abstraction (socket types, non-blocking, error handling,
  WSAStartup lifecycle)
- Add include/platform/process.hpp: CreateProcess/fork+exec
  abstraction for spawning ffplay subprocesses
- Update network module (tcp_socket, world_socket) to use
  portable socket helpers instead of raw POSIX calls
- Update audio module (music_manager, footstep_manager,
  activity_sound_manager) to use portable process helpers
  instead of fork/exec/kill/waitpid
- Replace hardcoded /tmp/ paths with std::filesystem::temp_directory_path()
- Link ws2_32 and SDL2main on Windows in CMakeLists.txt

include/audio/activity_sound_manager.hpp

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "audio/footstep_manager.hpp"
+#include "platform/process.hpp"
 #include <array>
 #include <chrono>
 #include <cstdint>
@@ -51,10 +52,10 @@ private:
 
     bool swimmingActive = false;
     bool swimMoving = false;
-    pid_t swimLoopPid = -1;
-    pid_t oneShotPid = -1;
-    std::string loopTempPath = "/tmp/wowee_swim_loop.wav";
-    std::string oneShotTempPath = "/tmp/wowee_activity.wav";
+    ProcessHandle swimLoopPid = INVALID_PROCESS;
+    ProcessHandle oneShotPid = INVALID_PROCESS;
+    std::string loopTempPath = platform::getTempFilePath("wowee_swim_loop.wav");
+    std::string oneShotTempPath = platform::getTempFilePath("wowee_activity.wav");
     std::mt19937 rng;
 
     std::chrono::steady_clock::time_point lastJumpAt{};

include/audio/footstep_manager.hpp

@@ -1,10 +1,10 @@
 #pragma once
 
+#include "platform/process.hpp"
 #include <cstdint>
 #include <random>
 #include <string>
 #include <vector>
-#include <sys/types.h>
 #include <chrono>
 
 namespace wowee {
@@ -56,8 +56,8 @@ private:
     SurfaceSamples surfaces[7];
     size_t sampleCount = 0;
 
-    std::string tempFilePath = "/tmp/wowee_footstep.wav";
-    pid_t playerPid = -1;
+    std::string tempFilePath = platform::getTempFilePath("wowee_footstep.wav");
+    ProcessHandle playerPid = INVALID_PROCESS;
     std::chrono::steady_clock::time_point lastPlayTime = std::chrono::steady_clock::time_point{};
 
     std::mt19937 rng;

include/audio/music_manager.hpp

@@ -1,5 +1,6 @@
 #pragma once
 
+#include "platform/process.hpp"
 #include <string>
 #include <vector>
 
@@ -31,7 +32,7 @@ private:
     pipeline::AssetManager* assetManager = nullptr;
     std::string currentTrack;
     std::string tempFilePath;
-    pid_t playerPid = -1;
+    ProcessHandle playerPid = INVALID_PROCESS;
     bool playing = false;
 
     // Crossfade state

include/network/net_platform.hpp

@@ -0,0 +1,122 @@
+#pragma once
+
+// Cross-platform socket abstractions for Windows (Winsock2) and POSIX.
+
+#ifdef _WIN32
+  #ifndef WIN32_LEAN_AND_MEAN
+    #define WIN32_LEAN_AND_MEAN
+  #endif
+  #include <winsock2.h>
+  #include <ws2tcpip.h>
+  #pragma comment(lib, "ws2_32.lib")
+
+  using socket_t  = SOCKET;
+  using ssize_t   = int;             // recv/send return int on Windows
+
+  inline constexpr socket_t INVALID_SOCK = INVALID_SOCKET;
+
+#else
+  #include <sys/socket.h>
+  #include <netinet/in.h>
+  #include <arpa/inet.h>
+  #include <netdb.h>
+  #include <unistd.h>
+  #include <fcntl.h>
+  #include <cerrno>
+
+  using socket_t = int;
+
+  inline constexpr socket_t INVALID_SOCK = -1;
+
+#endif
+
+#include <cstring>
+
+namespace wowee {
+namespace net {
+
+// ---- Winsock lifecycle (no-op on Linux) ----
+
+#ifdef _WIN32
+struct WinsockInit {
+    WinsockInit() {
+        WSADATA wsa;
+        WSAStartup(MAKEWORD(2, 2), &wsa);
+    }
+    ~WinsockInit() { WSACleanup(); }
+};
+// Call once at program start (e.g. as a static in Application).
+inline void ensureInit() {
+    static WinsockInit instance;
+}
+#else
+inline void ensureInit() {}
+#endif
+
+// ---- Portable helpers ----
+
+inline void closeSocket(socket_t s) {
+#ifdef _WIN32
+    closesocket(s);
+#else
+    close(s);
+#endif
+}
+
+inline bool setNonBlocking(socket_t s) {
+#ifdef _WIN32
+    u_long mode = 1;
+    return ioctlsocket(s, FIONBIO, &mode) == 0;
+#else
+    int flags = fcntl(s, F_GETFL, 0);
+    return fcntl(s, F_SETFL, flags | O_NONBLOCK) != -1;
+#endif
+}
+
+inline int lastError() {
+#ifdef _WIN32
+    return WSAGetLastError();
+#else
+    return errno;
+#endif
+}
+
+inline bool isWouldBlock(int err) {
+#ifdef _WIN32
+    return err == WSAEWOULDBLOCK;
+#else
+    return err == EAGAIN || err == EWOULDBLOCK;
+#endif
+}
+
+inline bool isInProgress(int err) {
+#ifdef _WIN32
+    return err == WSAEWOULDBLOCK || err == WSAEALREADY;
+#else
+    return err == EINPROGRESS;
+#endif
+}
+
+inline const char* errorString(int err) {
+#ifdef _WIN32
+    // Simple thread-local buffer for FormatMessage
+    thread_local char buf[256];
+    FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                   nullptr, err, 0, buf, sizeof(buf), nullptr);
+    return buf;
+#else
+    return strerror(err);
+#endif
+}
+
+// Portable send — Windows recv/send take char*, not void*.
+inline ssize_t portableSend(socket_t s, const uint8_t* data, size_t len) {
+    return ::send(s, reinterpret_cast<const char*>(data), static_cast<int>(len), 0);
+}
+
+inline ssize_t portableRecv(socket_t s, uint8_t* buf, size_t len) {
+    return ::recv(s, reinterpret_cast<char*>(buf), static_cast<int>(len), 0);
+}
+
+} // namespace net
+} // namespace wowee

include/network/tcp_socket.hpp

@@ -1,7 +1,7 @@
 #pragma once
 
 #include "network/socket.hpp"
-#include <sys/socket.h>
+#include "network/net_platform.hpp"
 
 namespace wowee {
 namespace network {
@@ -22,7 +22,7 @@ private:
     void tryParsePackets();
     size_t getExpectedPacketSize(uint8_t opcode);
 
-    int sockfd = -1;
+    socket_t sockfd = INVALID_SOCK;
     bool connected = false;
     std::vector<uint8_t> receiveBuffer;
 };

include/network/world_socket.hpp

@@ -2,6 +2,7 @@
 
 #include "network/socket.hpp"
 #include "network/packet.hpp"
+#include "network/net_platform.hpp"
 #include "auth/rc4.hpp"
 #include <functional>
 #include <vector>
@@ -73,7 +74,7 @@ private:
      */
     void tryParsePackets();
 
-    int sockfd = -1;
+    socket_t sockfd = INVALID_SOCK;
     bool connected = false;
     bool encryptionEnabled = false;
 

include/platform/process.hpp

@@ -0,0 +1,157 @@
+#pragma once
+
+// Cross-platform subprocess helpers for spawning ffplay (audio playback).
+// Linux: fork/exec/kill/waitpid.  Windows: CreateProcess/TerminateProcess.
+
+#include <string>
+#include <vector>
+
+#ifdef _WIN32
+  #ifndef WIN32_LEAN_AND_MEAN
+    #define WIN32_LEAN_AND_MEAN
+  #endif
+  #include <windows.h>
+
+  using ProcessHandle = HANDLE;
+  inline constexpr ProcessHandle INVALID_PROCESS = INVALID_HANDLE_VALUE;
+
+#else
+  #include <sys/types.h>
+  #include <sys/wait.h>
+  #include <unistd.h>
+  #include <csignal>
+
+  using ProcessHandle = pid_t;
+  inline constexpr ProcessHandle INVALID_PROCESS = -1;
+
+#endif
+
+#include <filesystem>
+
+namespace wowee {
+namespace platform {
+
+// Return a platform-appropriate temp file path for the given filename.
+inline std::string getTempFilePath(const std::string& filename) {
+    auto tmp = std::filesystem::temp_directory_path() / filename;
+    return tmp.string();
+}
+
+// Spawn ffplay with the given arguments. Returns process handle.
+// args should be the full argument list (e.g. {"-nodisp", "-autoexit", ...}).
+// The executable "ffplay" is resolved from PATH.
+inline ProcessHandle spawnProcess(const std::vector<std::string>& args) {
+#ifdef _WIN32
+    // Build command line string
+    std::string cmdline = "ffplay";
+    for (const auto& arg : args) {
+        cmdline += " ";
+        // Quote arguments that contain spaces
+        if (arg.find(' ') != std::string::npos) {
+            cmdline += "\"" + arg + "\"";
+        } else {
+            cmdline += arg;
+        }
+    }
+
+    STARTUPINFOA si{};
+    si.cb = sizeof(si);
+    // Hide the subprocess window and suppress stdout/stderr
+    si.dwFlags = STARTF_USESHOWWINDOW | STARTF_USESTDHANDLES;
+    si.wShowWindow = SW_HIDE;
+    si.hStdInput  = INVALID_HANDLE_VALUE;
+    si.hStdOutput = INVALID_HANDLE_VALUE;
+    si.hStdError  = INVALID_HANDLE_VALUE;
+
+    PROCESS_INFORMATION pi{};
+
+    // CreateProcessA needs a mutable char buffer for lpCommandLine
+    std::vector<char> cmdBuf(cmdline.begin(), cmdline.end());
+    cmdBuf.push_back('\0');
+
+    BOOL ok = CreateProcessA(
+        nullptr,          // lpApplicationName — resolve from PATH
+        cmdBuf.data(),    // lpCommandLine
+        nullptr, nullptr, // process/thread security
+        FALSE,            // inherit handles
+        CREATE_NO_WINDOW, // creation flags
+        nullptr, nullptr, // environment, working dir
+        &si, &pi
+    );
+
+    if (!ok) {
+        return INVALID_PROCESS;
+    }
+
+    // We don't need the thread handle
+    CloseHandle(pi.hThread);
+    return pi.hProcess;
+
+#else
+    pid_t pid = fork();
+    if (pid == 0) {
+        // Child process
+        setpgid(0, 0);
+        freopen("/dev/null", "w", stdout);
+        freopen("/dev/null", "w", stderr);
+
+        // Build argv for exec
+        std::vector<const char*> argv;
+        argv.push_back("ffplay");
+        for (const auto& arg : args) {
+            argv.push_back(arg.c_str());
+        }
+        argv.push_back(nullptr);
+
+        execvp("ffplay", const_cast<char* const*>(argv.data()));
+        _exit(1); // exec failed
+    }
+    return (pid > 0) ? pid : INVALID_PROCESS;
+#endif
+}
+
+// Kill a subprocess (and its children on Linux).
+inline void killProcess(ProcessHandle& handle) {
+    if (handle == INVALID_PROCESS) return;
+
+#ifdef _WIN32
+    TerminateProcess(handle, 0);
+    WaitForSingleObject(handle, 2000);
+    CloseHandle(handle);
+#else
+    kill(-handle, SIGTERM);  // kill process group
+    kill(handle, SIGTERM);
+    int status = 0;
+    waitpid(handle, &status, 0);
+#endif
+
+    handle = INVALID_PROCESS;
+}
+
+// Check if a process has exited. If so, clean up and set handle to INVALID_PROCESS.
+// Returns true if the process is still running.
+inline bool isProcessRunning(ProcessHandle& handle) {
+    if (handle == INVALID_PROCESS) return false;
+
+#ifdef _WIN32
+    DWORD result = WaitForSingleObject(handle, 0);
+    if (result == WAIT_OBJECT_0) {
+        // Process has exited
+        CloseHandle(handle);
+        handle = INVALID_PROCESS;
+        return false;
+    }
+    return true;
+#else
+    int status = 0;
+    pid_t result = waitpid(handle, &status, WNOHANG);
+    if (result == handle) {
+        handle = INVALID_PROCESS;
+        return false;
+    }
+    return true;
+#endif
+}
+
+} // namespace platform
+} // namespace wowee