docs overhaul, orientation API, fluid-sizing fixes, examples made honest

Documentation pass: every claim in docs/ and the meta files was audited against the source and the drift fixed — around ninety corrections. CONTRIBUTING and the CI workflow now run cargo test with --features test-support (the gated test_support module made both the documented commands and the CI build fail to compile), make example becomes make examples, make doctest-md and the debhelper requirement of make clean are documented, and patch shape asks for a CHANGELOG entry. theming.md loses the nonexistent surface.backdrop, gains the real gradient defaults (linear-rgb, oklab), the six slot variants including typography, the ten-field palette, a truthful effects-consumer table, the ThemePreference/from_hour API and a responsive-sizing note; the stale docstrings in src/theme that fed the drift are fixed too. architecture.md's "Known gaps" section is rewritten against reality (multi-touch slots, xdg-activation, a11y live regions and SetValue/Increment/Decrement are implemented), gains a module map, subsurfaces and window-lifecycle coverage, and correct crustace/loginmanager paths. widgets.md fixes the ten factual errors (stateless spinner, toast/combo via overlays(), tooltip hover contract, row has no max_width, scroll axes, multiline text_edit, dialog panic wording) and now states the column() 16 px default padding — the recurring ambush — plus row's differing 0 default and dialog's max_width. onboarding, README and cookbook get the remaining sweep: build/test instructions, complete example lists, img_widget, clipping-parity honesty, ~30 Hz software cap, read_rgba_pixels signature, tab indentation in snippets, and rustdoc-style links that rendered literally are gone everywhere. CHANGELOG is restructured per Keep a Changelog with the missing entries (window_resizable, claims_raw_touch, Row::align_top/fill_height, caret fixes, dependency pins) and the pad_v Added/Changed contradiction resolved.
New adaptive-layout API: ltk::orientation() with the Orientation enum, backed by viewport_size()/set_viewport_size — the runtime records the main surface's physical dimensions on every configure, before App::on_resize, so view() can branch a layout on portrait vs landscape without hand-tracking resizes. The portrait rule matches Length::orient (square counts as portrait); embedders driving core::UiSurface call set_viewport_size themselves. Documented in the crate root's responsive-design section and architecture.md.
Fluid-vs-fixed sizing fixes in widgets, all the same disease — fluid content inside a fixed-pixel box. TextEdit::fixed_width takes impl Into<Length> (f32 call sites keep compiling as px) and the time picker's digit fields move to Length::fluid( 72.0 ), matching their fluid font so digits can no longer outgrow the box. Dialog::max_width takes impl Into<Length> with a Length::fluid( 480.0 ) default so the card scales with the stock buttons inside it, and the card's interior no longer stacks the column() default 16 px padding on top of CARD_PADDING — that double inset squeezed the action row until its buttons clipped on narrow windows. App::on_pointer_axis now triggers a view rebuild and repaint; previously state mutated in the hook did not paint until the next unrelated event.
Examples reworked to be honest demos: responsive's mode/density controls become stock buttons in a grid/column so they follow the modes they demonstrate instead of overflowing; dialog's openers stack vertically, and the example gains the app-level ESC handler so the ESC chain closes an open dialog first and quits second; widgets' tab strip now switches real per-tab pages; carousel gains pointer/touch drag through the horizontal-swipe hooks (crustace's pager pattern), one-tile-per-detent mouse wheel, and snap math driven by the real surface width from on_resize instead of a hardcoded 800; clip_path arranges its cells by ltk::orientation() and sizes them from the counter-axis of the flow.

examples/responsive.rs

@@ -19,7 +19,7 @@
 use ltk::
 {
 	App, Element, Keysym, ButtonVariant, WidgetScaling,
-	button, checkbox, column, progress_bar, row, separator, slider, spacer, text, text_edit, toggle,
+	button, checkbox, column, grid, progress_bar, separator, slider, spacer, text, text_edit, toggle,
 	set_widget_scaling, set_density, density,
 };
 
@@ -81,21 +81,22 @@ impl App for ResponsiveApp
 
 		// Mode + density controls. Explicit sizes here so the controls stay
 		// stable while the demo widgets below react to the mode.
-		let controls = row::<Message>()
-			.spacing( 12.0 )
+		// Mode + density controls. Stock buttons like the demo widgets
+		// below, so they follow the active mode too. The switch gets the
+		// full width and the density pair half a cell each: every button
+		// clamps to its slot instead of overflowing a shared row, and the
+		// slots leave room for Physical-mode text at raised densities.
+		let controls = column::<Message>()
+			.padding( 0.0 )
+			.spacing( 8.0 )
 			.push( button::<Message>( "Switch mode".to_string() )
 				.variant( ButtonVariant::Primary )
-				.font_size( 16.0 )
-				.height( 44.0 )
 				.on_press( Message::SwitchMode ) )
-			.push( button::<Message>( "− density".to_string() )
-				.font_size( 16.0 )
-				.height( 44.0 )
-				.on_press( Message::DensityDown ) )
-			.push( button::<Message>( "＋ density".to_string() )
-				.font_size( 16.0 )
-				.height( 44.0 )
-				.on_press( Message::DensityUp ) );
+			.push( grid::<Message>( 2 )
+				.push( button::<Message>( "− density".to_string() )
+					.on_press( Message::DensityDown ) )
+				.push( button::<Message>( "＋ density".to_string() )
+					.on_press( Message::DensityUp ) ) );
 
 		// The demo widgets — NO explicit sizes, so they follow the mode.
 		let demo = column::<Message>()