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/TurnContextBuilder.hpp

@@ -0,0 +1,46 @@
+// 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 <QList>
+#include <QString>
+
+#include <optional>
+
+#include "session/TurnContext.hpp"
+#include "session/TurnContextPorts.hpp"
+
+namespace QodeAssist::Session {
+
+struct TurnContextRequest
+{
+    QString message;
+    QString basePrompt;
+    std::optional<QString> rolePrompt;
+    QList<QString> linkedFilePaths;
+};
+
+class TurnContextBuilder
+{
+public:
+    TurnContextBuilder(
+        const IProjectContextPort &project,
+        const ISkillsContextPort *skills,
+        const ILinkedFilesPort &linkedFiles);
+
+    TurnContextBuilder(IProjectContextPort &&, const ISkillsContextPort *, const ILinkedFilesPort &)
+        = delete;
+    TurnContextBuilder(const IProjectContextPort &, const ISkillsContextPort *, ILinkedFilesPort &&)
+        = delete;
+
+    TurnContext build(const TurnContextRequest &request) const;
+
+private:
+    const IProjectContextPort &m_project;
+    const ISkillsContextPort *m_skills = nullptr;
+    const ILinkedFilesPort &m_linkedFiles;
+};
+
+} // namespace QodeAssist::Session