Major refactoring - internal server state machine implemented

src/game_server/InternalGameServer.h

@@ -0,0 +1,47 @@
+#pragma once
+
+#include "IGameServer.h"
+
+namespace FRG {
+
+class Game;
+class Character;
+class Location;
+
+// In-process implementation used by single-player.  GameState exists exactly
+// once, here; clients see immutable snapshots and mutate it with typed commands.
+class InternalGameServer final : public IGameServer {
+public:
+	InternalGameServer();
+
+	std::shared_ptr<const GameSnapshot> snapshot() const override;
+	void submit(const GameCommand& command) override;
+	void update(std::int64_t deltaMs) override;
+	void save(nlohmann::json& out) const override;
+	void load(const nlohmann::json& in) override;
+
+private:
+	friend class Game;
+
+	// Transitional host operations are intentionally available only to Game,
+	// which owns location loading and old-save migration. They are never part of
+	// IGameServer and therefore cannot leak mutable state to UI/network clients.
+	GameState& hostState() { return state_; }
+	const GameState& hostState() const { return state_; }
+	std::unordered_map<std::string, std::shared_ptr<Location>>& runtimeLocations() { return runtimeLocations_; }
+	const std::unordered_map<std::string, std::shared_ptr<Location>>& runtimeLocations() const { return runtimeLocations_; }
+	void bindRuntimeLocation(const std::string& id, std::shared_ptr<Location> location);
+	void synchronizeRuntimeAuxiliaryState();
+	void applyStateToRuntime();
+	void markHostMutation();
+
+	GameSnapshot buildSnapshot() const;
+
+	GameState state_;
+	std::unordered_map<std::string, std::shared_ptr<Location>> runtimeLocations_;
+	std::uint64_t revision_ = 1;
+	mutable std::uint64_t cachedRevision_ = 0;
+	mutable std::shared_ptr<const GameSnapshot> cachedSnapshot_;
+};
+
+} // namespace FRG