refactor: Extract document reading to separate class (#127)

This decouples LLMClientInterface from Qt Creator text editor
implementation and allows to write tests

context/DocumentReaderQtCreator.hpp

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2025 Povilas Kanapickas
+ *
+ * This file is part of QodeAssist.
+ *
+ * QodeAssist is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * QodeAssist is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with QodeAssist. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include "IDocumentReader.hpp"
+
+#include <texteditor/textdocument.h>
+
+namespace QodeAssist::Context {
+
+class DocumentReaderQtCreator : public IDocumentReader
+{
+public:
+    DocumentInfo readDocument(const QString &path) const override
+    {
+        auto *textDocument = TextEditor::TextDocument::textDocumentForFilePath(
+            Utils::FilePath::fromString(path));
+        if (!textDocument) {
+            return {};
+        }
+        return {
+            .document = textDocument->document(),
+            .mimeType = textDocument->mimeType(),
+            .filePath = path};
+    }
+};
+
+} // namespace QodeAssist::Context