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/ChatView/LlmChatBackend.hpp

@@ -0,0 +1,69 @@
+// 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 <QHash>
+#include <QString>
+
+#include <LLMQore/BaseClient.hpp>
+
+#include "providers/Provider.hpp"
+#include "session/ChatBackend.hpp"
+#include "templates/IPromptProvider.hpp"
+
+namespace QodeAssist::Chat {
+
+class LlmChatBackend : public Session::ChatBackend
+{
+    Q_OBJECT
+
+public:
+    explicit LlmChatBackend(Templates::IPromptProvider *promptProvider, QObject *parent = nullptr);
+    ~LlmChatBackend() override;
+
+    void sendTurn(const Session::TurnRequest &request) override;
+    void cancel() override;
+
+    void setChatFilePath(const QString &filePath);
+    void clearToolSession(const QString &filePath);
+
+private:
+    void connectClient(Providers::Provider *provider);
+    void releaseRequest();
+    void bindToolSessions(Providers::Provider *provider);
+    QVector<LLMCore::Message> renderHistory(
+        const Session::ConversationHistory &history,
+        Providers::Provider *provider,
+        Templates::PromptTemplate *promptTemplate) const;
+    QVector<LLMCore::ImageAttachment> loadImagesFromStorage(
+        const QList<Session::ImageBlock> &storedImages) const;
+
+    void handleChunk(const QString &requestId, const QString &chunk);
+    void handleCompleted(const QString &requestId, const QString &fullText);
+    void handleFinalized(
+        const ::LLMQore::RequestID &requestId, const ::LLMQore::CompletionInfo &info);
+    void handleFailed(const QString &requestId, const QString &error);
+    void handleThinkingBlock(
+        const QString &requestId, const QString &thinking, const QString &signature);
+    void handleToolStarted(
+        const QString &requestId,
+        const QString &toolId,
+        const QString &toolName,
+        const QJsonObject &arguments);
+    void handleToolResult(
+        const QString &requestId,
+        const QString &toolId,
+        const QString &toolName,
+        const QString &toolOutput);
+
+    Templates::IPromptProvider *m_promptProvider = nullptr;
+    QString m_chatFilePath;
+
+    Providers::Provider *m_provider = nullptr;
+    QString m_requestId;
+    bool m_dropPreToolText = false;
+};
+
+} // namespace QodeAssist::Chat