Live mode: open a saved project, switch between open projects

open_project opens a .qet and makes it current, as File > Open does but
with no file dialog and no error windows: a missing, unreadable or
foreign file is refused in the answer. A project already open is only
made current. switch_project makes another open project current, by its
index or its file. status now lists every open project (index, title,
file, folios, unsaved changes, current), so the assistant sees what it
can switch to. MCP: qet_live_open_project, qet_live_switch_project; both
paths go through the workspace policy.

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

sources/scripting/liveserver.h

@@ -18,6 +18,7 @@
 #ifndef LIVESERVER_H
 #define LIVESERVER_H
 
+#include <QJsonArray>
 #include <QJsonObject>
 #include <QObject>
 #include <QPointer>
@@ -85,6 +86,9 @@ class LiveServer : public QObject
 		QJsonObject command(const QString &id);
 		QJsonObject showFolio(int folio);
 		QJsonObject newProject(const QJsonObject &request);
+		QJsonObject openProject(const QString &path);
+		QJsonObject switchProject(const QJsonObject &request);
+		QJsonArray openProjects() const;
 		QJsonObject undoLast();
 		QJsonObject screenshot();
 		bool confirm(const QString &name, const QString &source);