Script buttons: stored scripts become commands with an icon

Every .js file in the "scripts" folder of the user's data folder that
starts with a // ==QETScript== header becomes a command: in Projet >
Scripts, as a button on a new Scripts toolbar, and, because it is
registered with ShortcutManager as diagrameditor.script.<file name>, in
the shortcut settings, the shortcut bar (S) and command search. The
header gives its name, icon (a file next to the script or a theme icon;
a tile with its initials otherwise), tooltip, default shortcut and when
it is enabled (always, with a selection, with a conductor selected).

The folder is watched, so a script added, edited or deleted while QET is
open appears, changes or goes without a restart. A file with a header
that cannot be used gets no button; the Scripts menu lists it with the
reason. The menu also opens the folder, and holds "Exécuter un script…".

A click runs the script on the current project as one undo step named
after it, and asks to switch scripting on first, like "Exécuter un
script…" does: scripting stays off by default.

ShortcutManager::unregisterAction() takes a command out of the lists
when its script is deleted, and lets it come back under a new name.

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

sources/scripting/scriptheader.h

@@ -0,0 +1,118 @@
+/*
+	Copyright 2006-2026 The QElectroTech Team
+	This file is part of QElectroTech.
+
+	QElectroTech is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 2 of the License, or
+	(at your option) any later version.
+
+	QElectroTech is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
+*/
+#ifndef SCRIPTHEADER_H
+#define SCRIPTHEADER_H
+
+#include <QRegularExpression>
+#include <QString>
+#include <QStringList>
+
+/**
+	@brief The ScriptHeader struct
+	How a stored script's button looks, read from a comment block at the top
+	of the .js file itself, so one file is all there is to write by hand,
+	to share, or for an assistant to create:
+
+	@code
+	// ==QETScript==
+	// @name     Add revision note
+	// @icon     note.svg           (a file next to the script, or builtin:<theme icon>)
+	// @tooltip  Puts a "Rev A" note on the folio on screen
+	// @shortcut Ctrl+Alt+R
+	// @context  canvas             (canvas, selection or conductor)
+	// @api      1
+	// ==/QETScript==
+	@endcode
+
+	Only @name is required. An unknown key is an error rather than ignored:
+	a misspelt "@shortcut" that silently did nothing would be harder to find
+	than a script refused with the line that is wrong.
+
+	Header-only, with no QElectroTech dependency, so it is tested on its own.
+*/
+struct ScriptHeader
+{
+	QString id;        ///< file name without .js; the action id is diagrameditor.script.<id>
+	QString name;
+	QString icon;
+	QString tooltip;
+	QString shortcut;  ///< as QKeySequence::fromString() reads it
+	QString context = QStringLiteral("canvas");
+	int api = 1;
+	QString error;     ///< empty if the header is usable
+
+	bool isValid() const { return error.isEmpty(); }
+
+	static QStringList contexts()
+	{
+		return {QStringLiteral("canvas"), QStringLiteral("selection"),
+			QStringLiteral("conductor")};
+	}
+
+	/**
+		@brief parse
+		@param text : the whole script
+		@param id : the script's file name without its extension
+	*/
+	static ScriptHeader parse(const QString &text, const QString &id)
+	{
+		ScriptHeader h;
+		h.id = id;
+		static const QRegularExpression block(
+			QStringLiteral("//\\s*==QETScript==\\s*\\n(.*?)//\\s*==/QETScript=="),
+			QRegularExpression::DotMatchesEverythingOption);
+		const QRegularExpressionMatch m = block.match(text);
+		if (!m.hasMatch()) {
+			h.error = QStringLiteral("no // ==QETScript== header");
+			return h;
+		}
+		static const QRegularExpression line_re(
+			QStringLiteral("^\\s*//\\s*@(\\w+)\\s+(.*?)\\s*$"));
+		const QStringList lines = m.captured(1).split(QLatin1Char('\n'));
+		for (const QString &line : lines) {
+			const QRegularExpressionMatch lm = line_re.match(line);
+			if (!lm.hasMatch()) {
+				continue;
+			}
+			const QString key = lm.captured(1);
+			const QString value = lm.captured(2);
+			if (key == QLatin1String("name")) h.name = value;
+			else if (key == QLatin1String("icon")) h.icon = value;
+			else if (key == QLatin1String("tooltip")) h.tooltip = value;
+			else if (key == QLatin1String("shortcut")) h.shortcut = value;
+			else if (key == QLatin1String("context")) h.context = value;
+			else if (key == QLatin1String("api")) h.api = value.toInt();
+			else {
+				h.error = QStringLiteral("unknown header key @%1").arg(key);
+				return h;
+			}
+		}
+		if (h.name.isEmpty()) {
+			h.error = QStringLiteral("@name is required");
+		} else if (!contexts().contains(h.context)) {
+			h.error = QStringLiteral("@context must be one of: %1")
+					.arg(contexts().join(QStringLiteral(", ")));
+		} else if (h.api != 1) {
+			h.error = QStringLiteral("@api %1 is not supported by this "
+						 "version (1 is)").arg(h.api);
+		}
+		return h;
+	}
+};
+
+#endif // SCRIPTHEADER_H