fix: the presenter stops insisting on fullscreen after a few refusals

The slideshow re-asserts fullscreen when a compositor takes it away,
which is what keeps a teacher from being left looking at the library
beside their slides. A compositor that granted it and revoked it
repeatedly would have had this asking forever, in the middle of a Bible
study.

It gives up after five goes. The slides are still on the screen and
Escape still works; only the insisting stops, which is a far better
failure than a window fighting a compositor in front of a room.

Co-Authored-By: Claude Opus 5 <[email protected]>

scripts/classroom-presentations

@@ -138,6 +138,9 @@ class Presenter(Gtk.Window):
         self.page = min(max(start_page, 1), presentation.pages or 1)
         self.counted = False
         self.finished = False
+        # How many times fullscreen has been asked for without it
+        # sticking. See _state.
+        self.refused = 0
 
         self.set_app_paintable(True)
         self.fullscreen()
@@ -172,11 +175,23 @@ class Presenter(Gtk.Window):
         So fullscreen is re-asserted rather than assumed, for as long as
         the presentation is running. It stops the moment Escape is
         pressed, so this can never fight the teacher's way out.
+
+        And it gives up after a few goes. A compositor that keeps
+        granting fullscreen and taking it away again would otherwise have
+        this asking forever, in the middle of a Bible study, which is a
+        worse failure than the window being the wrong size. After that
+        the slides are still on the screen and Escape still works — only
+        the insisting stops.
         """
         if self.finished:
             return False
 
-        if not (event.new_window_state & Gdk.WindowState.FULLSCREEN):
+        if event.new_window_state & Gdk.WindowState.FULLSCREEN:
+            self.refused = 0
+            return False
+
+        if self.refused < 5:
+            self.refused += 1
             self.fullscreen()
 
         return False