Scripting is off until asked for, and says how to turn it on

A script reaches the whole project and, through the export calls, the
filesystem. That is a capability most people installing an electrical CAD
program never asked for, and leaving it on by default hands it to them
anyway. So QET_HAS_SCRIPTING builds now ship with it switched off.

QetSettings::scriptingEnabled() is the single answer, read by all three
places that need it, with QET_ENABLE_SCRIPTING=1 overriding the stored
value. The override is not decoration: a CI job or a batch run has no
dialog to tick, and a machine whose HOME is created fresh for each run has
nowhere to keep the setting either. It beats a stored "false" on purpose,
so a box unticked once cannot lock a build server out of --run for good.
Only the exact value "1" counts.

  --run          refuses with exit 3 and a message naming both ways in.
  Projet > Exécuter un script...  asks once, and turns the setting on if
                 the answer is yes. Asking beats grey: a disabled menu
                 entry says something exists and nothing about how to have
                 it, and this is the pattern people already know from
                 macro security in office software.
  Configurer QElectroTech > Général > Projets  has the checkbox, for
                 turning it back off. While the environment forces
                 scripting on, the box is disabled and says why, and
                 applyConf() then leaves the stored value alone rather
                 than quietly overwriting it.

runOnProject() checks as well, after both callers have. It is the one
function that actually evaluates JavaScript, so it is the one place a
future caller cannot forget to ask; the callers check first only to give a
better answer than it can.

Verified on the built binary, all four states, with an isolated HOME:

  stored   env  result
  absent    -   refused, exit 3
  true      -   script runs, exit 0
  false     -   refused, exit 3
  false     1   script runs, exit 0

tst_scriptingsetting covers the same matrix hermetically, in its own
QSettings scope, and was mutation-checked: flipping the default to true
turns defaultsToOff() red.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

sources/scripting/qetscripting.cpp

@@ -20,6 +20,7 @@
 #include "qetscriptapi.h"
 #include "../qetmessagebox.h"
 #include "../qetproject.h"
+#include "../utils/qetsettings.h"
 
 #include <QFile>
 #include <QFileInfo>
@@ -48,8 +49,33 @@ bool isRunRequest(const QStringList &args)
 
 #ifdef QET_HAS_SCRIPTING
 
+namespace {
+	/**
+		@brief refusalMessage
+		What to tell somebody whose script was not run, and how to change
+		that. Written once because the command line and the graphical
+		editor both need to say it, and an explanation that names only one
+		of the two ways out sends half the people down the wrong path.
+	*/
+	QString refusalMessage()
+	{
+		return QObject::tr(
+			"Les scripts sont désactivés.\n\n"
+			"Un script a accès à l'ensemble du projet et peut écrire des "
+			"fichiers, aussi cette fonction est-elle désactivée par défaut.\n\n"
+			"Pour l'activer : Configurer QElectroTech > Général > Projets, "
+			"ou définir la variable d'environnement QET_ENABLE_SCRIPTING=1 "
+			"pour une exécution sans interface (CI, traitement par lot).");
+	}
+}
+
 int run(const QStringList &args)
 {
+	if (!QetSettings::scriptingEnabled()) {
+		err << refusalMessage() << "\n";
+		return 3;
+	}
+
 	const int idx = args.indexOf(QStringLiteral("--run"));
 	const QString script_path = args.value(idx + 1);
 	const QString project_path = args.value(idx + 2);
@@ -88,6 +114,20 @@ namespace {
 
 bool runOnProject(const QString &scriptPath, QETProject *project, DiagramView *view)
 {
+	// Checked here as well as at each caller, deliberately: this is the
+	// one function that actually evaluates JavaScript, so it is the one
+	// place a future caller cannot forget to ask. The callers check first
+	// only to give a better answer than this one can -- a usable exit code
+	// on the command line, an offer to switch the setting on in the editor.
+	if (!QetSettings::scriptingEnabled()) {
+		err << refusalMessage() << "\n";
+		if (view) {
+			QET::QetMessageBox::warning(nullptr, QObject::tr("Script"),
+						    refusalMessage());
+		}
+		return false;
+	}
+
 	QFile file(scriptPath);
 	if (!file.open(QIODevice::ReadOnly | QIODevice::Text)) {
 		err << "Cannot open script: " << scriptPath << "\n";