Исправлен белый экран предпросмотра: CodeBlock отдельный компонент

- CodeBlock.qml: Qt.rgba вместо "rgba(...)", убран lineHeight, contentHeight для ScrollView, width via availableWidth
- MarkdownView.qml: ListModel с полными ролями (codeText/highlightedText), delegate без required model, Column anchors.top/left/right, parseBlocks сохраняет codeBlocks
- MdParser: parseBlocks с QRegularExpression и сохранением codeBlocks, forceDark highlight
- mdparser_test: проверка parseBlocks 3 блока
- ctest 21/21, offscreen/cocoa RUNNING OK, Flora.app 180М

qml/panels/MarkdownView.qml

@@ -43,14 +43,16 @@ Item {
         Repeater {
             model: blocksModel
             delegate: Item {
+                required property var model
+                required property int index
                 width: parent.width
                 height: childrenRect.height
                 property string blockType: model.type || ""
                 property string blockHtml: model.html || ""
-                property string blockCode: model.code || ""
+                property string blockCode: model.codeText || ""
                 property string blockLang: model.language || "text"
                 property string blockCodeId: model.codeId || ""
-                property string blockHighlighted: model.highlighted || ""
+                property string blockHighlighted: model.highlightedText || ""
                 // HTML block
                 Text {
                     visible: blockType === "html" && blockHtml