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/HistoryProjection.hpp

@@ -0,0 +1,51 @@
+// 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 <QList>
+#include <QString>
+
+#include <optional>
+
+#include "session/ConversationHistory.hpp"
+
+namespace QodeAssist::Session {
+
+enum class RowKind { User, Assistant, System, Tool, FileEdit, Thinking };
+
+struct MessageRow
+{
+    RowKind kind = RowKind::User;
+    QString id;
+    QString content;
+    bool redacted = false;
+    QString signature;
+    QString toolName;
+    QJsonObject toolArguments;
+    QString toolResult;
+    QList<AttachmentBlock> attachments;
+    QList<ImageBlock> images;
+    Usage usage;
+
+    bool operator==(const MessageRow &other) const = default;
+
+    friend QDebug operator<<(QDebug debug, const MessageRow &row)
+    {
+        return debug.nospace() << "Row(kind=" << int(row.kind) << ", id=" << row.id
+                               << ", content=" << row.content << ", sig=" << row.signature
+                               << ", redacted=" << row.redacted << ", tool=" << row.toolName
+                               << ", args=" << row.toolArguments << ", result=" << row.toolResult
+                               << ", attachments=" << row.attachments << ", images=" << row.images
+                               << ", " << row.usage << ")";
+    }
+};
+
+std::optional<MessageRow> projectBlockToRow(const Message &message, const ContentBlock &block);
+QList<MessageRow> projectMessageToRows(const Message &message);
+QList<MessageRow> projectToRows(const ConversationHistory &history);
+ConversationHistory buildFromRows(const QList<MessageRow> &rows);
+
+} // namespace QodeAssist::Session