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/separator/tests.rs

@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: LGPL-2.1-only
+// Copyright (C) 2026 Liberux Labs, S. L. <info@liberux.net>
+
+use super::*;
+
+#[test]
+fn default_thickness()
+{
+	let s = separator();
+	assert_eq!( s.thickness, theme::THICKNESS );
+}
+
+#[test]
+fn preferred_height_includes_padding()
+{
+	let s = separator();
+	let ( _, h ) = s.preferred_size( 200.0 );
+	assert_eq!( h, theme::THICKNESS + theme::PAD_V * 2.0 );
+}