feat: add support acp in common chat (#369)

sources/session/BlockCodec.cpp

@@ -0,0 +1,38 @@
+// Copyright (C) 2026 Petr Mironychev
+// SPDX-License-Identifier: GPL-3.0-or-later
+// Additional attribution terms under GPLv3 §7(b) apply — see LICENSE
+
+#include "session/BlockCodec.hpp"
+
+#include <QJsonDocument>
+
+namespace QodeAssist::Session {
+
+QList<QLatin1StringView> knownPayloadMarkers()
+{
+    return {payloadMarkers.begin(), payloadMarkers.end()};
+}
+
+bool hasPayloadMarker(QLatin1StringView marker, const QString &text)
+{
+    return text.startsWith(marker);
+}
+
+QString encodeMarkerPayload(QLatin1StringView marker, const QJsonObject &payload)
+{
+    return marker + QString::fromUtf8(QJsonDocument(payload).toJson(QJsonDocument::Compact));
+}
+
+std::optional<QJsonObject> decodeMarkerPayload(QLatin1StringView marker, const QString &text)
+{
+    if (!hasPayloadMarker(marker, text))
+        return std::nullopt;
+
+    const QJsonDocument document = QJsonDocument::fromJson(text.mid(marker.size()).toUtf8());
+    if (!document.isObject())
+        return std::nullopt;
+
+    return document.object();
+}
+
+} // namespace QodeAssist::Session