Add plugin receive loop & remote player state

Add a networking receive loop and in-plugin remote-player storage. Introduces F4TRemotePlayerState (header + implementation) to track assigned playerId and remote player snapshots with thread-safe access. Expands F4TNetworking to start/stop a background receive thread, parse newline-separated JSON packets (welcome, transform, disconnect), validate fields, update remote state, throttle logs, and handle socket/thread synchronization. Add nlohmann_json to xmake and plugin build. Update docs and dev log to reflect the new receive behavior and current prototype scope.

plugin/src/F4TRemotePlayerState.cpp

@@ -0,0 +1,73 @@
+#include "pch.h"
+
+#include "F4TRemotePlayerState.h"
+
+#include <mutex>
+#include <optional>
+#include <unordered_map>
+#include <vector>
+
+namespace
+{
+	std::mutex g_stateMutex;
+	std::optional<std::uint32_t> g_assignedPlayerId;
+	std::unordered_map<std::uint32_t, F4T::RemotePlayerState::RemotePlayerState> g_remotePlayers;
+}
+
+namespace F4T::RemotePlayerState
+{
+	void SetAssignedPlayerId(std::uint32_t a_playerId)
+	{
+		const std::scoped_lock lock(g_stateMutex);
+		g_assignedPlayerId = a_playerId;
+	}
+
+	std::optional<std::uint32_t> GetAssignedPlayerId()
+	{
+		const std::scoped_lock lock(g_stateMutex);
+		return g_assignedPlayerId;
+	}
+
+	bool IsAssignedPlayerId(std::uint32_t a_playerId)
+	{
+		const std::scoped_lock lock(g_stateMutex);
+		return g_assignedPlayerId.has_value() && *g_assignedPlayerId == a_playerId;
+	}
+
+	void ClearAssignedPlayerId()
+	{
+		const std::scoped_lock lock(g_stateMutex);
+		g_assignedPlayerId.reset();
+	}
+
+	void UpdateRemotePlayer(RemotePlayerState a_state)
+	{
+		const std::scoped_lock lock(g_stateMutex);
+		g_remotePlayers[a_state.playerId] = std::move(a_state);
+	}
+
+	bool RemoveRemotePlayer(std::uint32_t a_playerId)
+	{
+		const std::scoped_lock lock(g_stateMutex);
+		return g_remotePlayers.erase(a_playerId) > 0;
+	}
+
+	void ClearRemotePlayers()
+	{
+		const std::scoped_lock lock(g_stateMutex);
+		g_remotePlayers.clear();
+	}
+
+	std::vector<RemotePlayerState> GetRemotePlayerSnapshot()
+	{
+		const std::scoped_lock lock(g_stateMutex);
+
+		std::vector<RemotePlayerState> snapshot;
+		snapshot.reserve(g_remotePlayers.size());
+		for (const auto& [_, player] : g_remotePlayers) {
+			snapshot.push_back(player);
+		}
+
+		return snapshot;
+	}
+}