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/TurnContext.hpp

@@ -0,0 +1,57 @@
+// 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>
+
+namespace QodeAssist::Session {
+
+struct ProjectInfo
+{
+    bool available = false;
+    QString displayName;
+    QString sourceRoot;
+    std::optional<QString> buildDirectory;
+
+    bool operator==(const ProjectInfo &other) const = default;
+};
+
+struct InvokedSkill
+{
+    QString name;
+    QString body;
+
+    bool operator==(const InvokedSkill &other) const = default;
+};
+
+struct LinkedFile
+{
+    QString fileName;
+    QString content;
+
+    bool operator==(const LinkedFile &other) const = default;
+};
+
+struct TurnContext
+{
+    QString basePrompt;
+    std::optional<QString> rolePrompt;
+    ProjectInfo project;
+    QString projectRules;
+    QString alwaysOnSkills;
+    QString skillsCatalog;
+    QList<InvokedSkill> invokedSkills;
+    QList<QString> linkedFilePaths;
+    QList<LinkedFile> linkedFiles;
+
+    bool operator==(const TurnContext &other) const = default;
+};
+
+QString renderSystemPrompt(const TurnContext &context);
+
+} // namespace QodeAssist::Session