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/window_button/tests.rs

@@ -0,0 +1,50 @@
+// SPDX-License-Identifier: LGPL-2.1-only
+// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>
+
+use super::*;
+use crate::render::Canvas;
+
+#[ test ]
+fn default_size_is_decoration_sized()
+{
+	let canvas = Canvas::new( 100, 100 );
+	let b = window_button::<()>( WindowButtonKind::Close );
+	assert_eq!( b.preferred_size( 100.0, &canvas ), ( theme::SIZE, theme::SIZE ) );
+}
+
+#[ test ]
+fn controls_has_three_children()
+{
+	let controls = window_controls::<()>(
+		Some( () ), WindowButtonKind::Maximize, Some( () ), Some( () ),
+	);
+	assert_eq!( controls.children.len(), 3 );
+}
+
+#[ test ]
+fn icon_names_resolve_each_kind_to_the_window_catalogue()
+{
+	// Lock the catalogue paths so a future rename of the on-disk
+	// SVG (e.g. close.svg → x.svg) breaks this test instead of
+	// silently falling back to the programmatic glyph at runtime.
+	assert_eq!( icon_name( WindowButtonKind::Minimize ), "window/minimize" );
+	assert_eq!( icon_name( WindowButtonKind::Maximize ), "window/maximize" );
+	assert_eq!( icon_name( WindowButtonKind::Restore  ), "window/restore"  );
+	assert_eq!( icon_name( WindowButtonKind::Close    ), "window/close"    );
+}
+
+#[ test ]
+fn paint_bounds_unchanged_after_glyph_refactor()
+{
+	// The SVG glyph paints inside the button rect just like the
+	// programmatic one did, so paint_bounds must stay equal to
+	// the previous value (rect expanded by the focus-ring slack).
+	let b = window_button::<()>( WindowButtonKind::Close );
+	let rect = Rect { x: 10.0, y: 10.0, width: 36.0, height: 36.0 };
+	let bounds = b.paint_bounds( rect );
+	let slack = theme::FOCUS_W * 1.5 + 2.0;
+	assert!( ( bounds.x - ( rect.x - slack ) ).abs() < 0.01 );
+	assert!( ( bounds.y - ( rect.y - slack ) ).abs() < 0.01 );
+	assert!( ( bounds.width  - ( rect.width  + slack * 2.0 ) ).abs() < 0.01 );
+	assert!( ( bounds.height - ( rect.height + slack * 2.0 ) ).abs() < 0.01 );
+}