refactor: Decoupling chat architecture (#367)

* refactor: Migrate tests to Qt Creator plugin framework and update llmqore transports

* refactor: Move conversation history into IDE-free session library

* refactor: Extract turn context assembly behind injected ports

* build: Add RunQodeAssistTests target for the plugin test suite

* refactor: Route the chat through a Session and ChatBackend seam

sources/session/HistorySerializer.hpp

@@ -0,0 +1,27 @@
+// Copyright (C) 2026 Petr Mironychev
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Additional attribution terms under GPLv3 §7(b) apply — see LICENSE
+
+#pragma once
+
+#include <QJsonObject>
+#include <QString>
+
+#include <optional>
+
+#include "session/ConversationHistory.hpp"
+
+namespace QodeAssist::Session {
+
+class HistorySerializer
+{
+public:
+    static QString currentVersion();
+    static bool isSupportedVersion(const QString &version);
+
+    static QJsonObject toJson(const ConversationHistory &history);
+    static std::optional<ConversationHistory> fromJson(
+        const QJsonObject &root, int *droppedBlocks = nullptr);
+};
+
+} // namespace QodeAssist::Session