Scripting: qet.apiSignatures(), the calls a script can make

Read from the meta-object, so the list is the one the running build has:
for someone writing a script, and for an assistant that has to write one
without the source at hand.

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

sources/scripting/qetscriptapi.h

@@ -579,6 +579,9 @@ class QetScriptApi : public QObject
 		// -- logging: a script has no console of its own --
 		Q_INVOKABLE void log(const QString &message);
 
+		// -- what a script can call, read from this class itself --
+		Q_INVOKABLE QStringList apiSignatures() const;
+
 		void setUndoGrouped(bool grouped);
 
 	private: