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.

src/types.rs

@@ -703,6 +703,48 @@ pub fn density() -> f32
 	f32::from_bits( DENSITY_BITS.load( Ordering::Relaxed ) )
 }
 
+/// Orientation of the main surface, derived from the dimensions recorded
+/// by [`set_viewport_size`].
+#[ derive( Clone, Copy, Debug, PartialEq, Eq ) ]
+pub enum Orientation
+{
+	Portrait,
+	Landscape,
+}
+
+static VIEWPORT_W: AtomicU32 = AtomicU32::new( 0 );
+static VIEWPORT_H: AtomicU32 = AtomicU32::new( 0 );
+
+/// Record the main surface's physical dimensions. The runtime calls this
+/// on every configure, before `App::on_resize`; embedders driving
+/// [`core::UiSurface`](crate::core::UiSurface) directly should call it
+/// themselves if they want [`viewport_size`] / [`orientation`] to reflect
+/// their surface.
+pub fn set_viewport_size( width: u32, height: u32 )
+{
+	VIEWPORT_W.store( width,  Ordering::Relaxed );
+	VIEWPORT_H.store( height, Ordering::Relaxed );
+}
+
+/// Physical dimensions of the main surface as of the last configure.
+/// `( 0, 0 )` before the first one.
+pub fn viewport_size() -> ( u32, u32 )
+{
+	( VIEWPORT_W.load( Ordering::Relaxed ), VIEWPORT_H.load( Ordering::Relaxed ) )
+}
+
+/// Orientation of the main surface: [`Orientation::Landscape`] when wider
+/// than tall, [`Orientation::Portrait`] otherwise (square counts as
+/// portrait, matching [`Length::orient`]'s resolution rule). Usable
+/// straight from `view()` to pick a row or a column arrangement without
+/// tracking `on_resize` by hand — the runtime rebuilds the view on every
+/// resize, so a layout branched on this follows the window live.
+pub fn orientation() -> Orientation
+{
+	let ( w, h ) = viewport_size();
+	if w > h { Orientation::Landscape } else { Orientation::Portrait }
+}
+
 /// How a stock widget adapts its intrinsic geometry to the display when the
 /// app does not override it. The two modes ltk offers, chosen per process
 /// with [`set_widget_scaling`]: