refactor: split every monolithic module into focused submodules

Each source file that had grown beyond a single concern is replaced by an identically-named directory containing focused submodules. `src/event_loop/mod.rs` (878 lines) becomes a directory with clipboard, context_menu, cursor_shape, drag, focus, handlers, invalidation, overlays_reconcile, repeat, run, surface, text_editing, and tooltip. Every widget, input handler, and theme component follows the same split. Public interfaces are unchanged — only the internal file layout moves.
image bumped from 0.25.2 to 0.25.9.

src/widget/viewport/tests.rs

@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: LGPL-2.1-only
+// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>
+
+use super::*;
+use crate::layout::spacer::spacer;
+use crate::render::Canvas;
+
+fn make_canvas() -> Canvas { Canvas::new( 800, 600 ) }
+
+#[ test ]
+fn new_defaults_are_unset_dimensions_and_no_fade()
+{
+	let v = Viewport::<()>::new( spacer() );
+	assert!( v.width.is_none() );
+	assert!( v.height.is_none() );
+	assert_eq!( v.fade_bottom, 0.0 );
+}
+
+#[ test ]
+fn width_builder_clamps_negative_to_zero()
+{
+	let v = Viewport::<()>::new( spacer() ).width( -50.0 );
+	assert_eq!( v.width, Some( 0.0 ) );
+}
+
+#[ test ]
+fn height_builder_clamps_negative_to_zero()
+{
+	let v = Viewport::<()>::new( spacer() ).height( -10.0 );
+	assert_eq!( v.height, Some( 0.0 ) );
+}
+
+#[ test ]
+fn fade_bottom_clamps_negative_to_zero()
+{
+	let v = Viewport::<()>::new( spacer() ).fade_bottom( -1.0 );
+	assert_eq!( v.fade_bottom, 0.0 );
+}
+
+#[ test ]
+fn fade_bottom_accepts_positive_pixel_count()
+{
+	let v = Viewport::<()>::new( spacer() ).fade_bottom( 16.0 );
+	assert_eq!( v.fade_bottom, 16.0 );
+}
+
+#[ test ]
+fn explicit_dimensions_override_child_intrinsic_size()
+{
+	let v = Viewport::<()>::new( spacer().width( 99.0 ).height( 99.0 ) )
+		.width( 200.0 )
+		.height( 80.0 );
+	let canvas = make_canvas();
+	let ( w, h ) = v.preferred_size( 600.0, &canvas );
+	assert_eq!( w, 200.0 );
+	assert_eq!( h,  80.0 );
+}
+
+#[ test ]
+fn unset_width_falls_through_to_max_width()
+{
+	let v = Viewport::<()>::new( spacer().height( 40.0 ) );
+	let canvas = make_canvas();
+	let ( w, _ ) = v.preferred_size( 400.0, &canvas );
+	assert_eq!( w, 400.0 );
+}
+
+#[ test ]
+fn unset_height_falls_through_to_child_intrinsic_height()
+{
+	let v = Viewport::<()>::new( spacer().height( 75.0 ) );
+	let canvas = make_canvas();
+	let ( _, h ) = v.preferred_size( 400.0, &canvas );
+	assert_eq!( h, 75.0 );
+}