Scripting: qet.currentFolio(), and one undo step per script run in the editor

A script started from the editor had no way to know which folio is on
screen, and each qet.* call was its own undo step, so a script that adds
twenty items needed twenty Ctrl+Z to take back.

qet.currentFolio() returns the folio shown in the editor; through --run,
which has no view, the first folio, or -1 when there is none.

A run from the editor is now one undo macro, named after the script. A
run that changed nothing leaves no empty entry behind. qet.undo() and
qet.redo() inside a grouped run say why they cannot work (QUndoStack
ignores them inside a macro) instead of failing silently. --run is
unchanged: one step per call, so scripts that call qet.undo() keep
working.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

sources/scripting/qetscriptapi.h

@@ -354,6 +354,7 @@ class QetScriptApi : public QObject
 		Q_INVOKABLE QString projectTitle() const;
 		Q_INVOKABLE QString filePath() const;
 		Q_INVOKABLE int folioCount() const;
+		Q_INVOKABLE int currentFolio() const;
 		Q_INVOKABLE QString folioTitle(int index) const;
 		Q_INVOKABLE QString folioUuid(int index) const;
 		Q_INVOKABLE int folioIndex(const QString &uuid) const;
@@ -578,6 +579,8 @@ class QetScriptApi : public QObject
 		// -- logging: a script has no console of its own --
 		Q_INVOKABLE void log(const QString &message);
 
+		void setUndoGrouped(bool grouped);
+
 	private:
 		bool runFlag(const QString &flag, const QStringList &args);
 		Element *findElement(int folioIndex, const QString &elementUuid) const;
@@ -597,6 +600,7 @@ class QetScriptApi : public QObject
 
 		QETProject *m_project;
 		DiagramView *m_view;
+		bool m_undo_grouped = false;
 		QString m_query_error;
 };