Live mode: an AI assistant acts on the open project while the user watches

A new setting, Configurer QElectroTech > Général > "Autoriser un assistant
IA à agir sur le projet ouvert", off by default. Off, nothing changes:
no channel is opened. On, every start shows a warning first -- Continuer,
Pas pour cette session, or Désactiver -- and nothing can connect until
the user answers Continuer. It waits for any other start-up question to
be answered, so the two never stack.

Accepted, LiveServer opens a local socket only the user's account can
use, with a random name and token written to live-session.json in the
data folder for the qet MCP server, and removed when the channel closes.
One JSON request per line: status (project, folio on screen, selection,
last undo step, stored scripts), run_script and run_stored. Requests are
queued out of the socket handler before they run (the lesson of PR #861).

Each run is one undo step named "Assistant : <name>". The status bar
shows the mode and the assistant's last action with a ✓ or ✗ and the
time, and an Arrêter button that closes the channel for the session.
Unticking the setting closes it at once.

QetScripting::runSource() runs script text and, for a live run, returns
what qet.log() wrote, the error with its line and the undo step instead
of showing boxes; qet.showMessage() is logged rather than opening a box
nobody asked for.

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

sources/scripting/qetscriptapi.h

@@ -583,6 +583,7 @@ class QetScriptApi : public QObject
 		Q_INVOKABLE QStringList apiSignatures() const;
 
 		void setUndoGrouped(bool grouped);
+		void setLive(QStringList *log);
 
 	private:
 		bool runFlag(const QString &flag, const QStringList &args);
@@ -604,6 +605,7 @@ class QetScriptApi : public QObject
 		QETProject *m_project;
 		DiagramView *m_view;
 		bool m_undo_grouped = false;
+		QStringList *m_live_log = nullptr;	///< set for a live run: log() and showMessage() go here
 		QString m_query_error;
 };