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/widget/text_edit/mod.rs

@@ -143,7 +143,7 @@ pub struct TextEdit<Msg: Clone>
 	/// default for forms but wrong when the field needs to be sized
 	/// to fit a fixed number of glyphs (date / time pickers, inline
 	/// numeric inputs).
-	pub( crate ) fixed_width: Option<f32>,
+	pub( crate ) fixed_width: Option<Length>,
 	/// Font size in pixels for the single-line draw path. `0.0` (the
 	/// Label font size. `None` follows the process [`crate::WidgetScaling`]
 	/// mode at the theme default (via [`crate::Canvas::font_px`]); a
@@ -299,10 +299,12 @@ impl<Msg: Clone> TextEdit<Msg>
 	}
 
 	/// Override the preferred width reported to the parent layout.
-	/// Pass `None` (default) to fall back to claiming `max_width`.
-	pub fn fixed_width( mut self, w: f32 ) -> Self
+	/// Accepts logical `f32` pixels or any [`Length`] — pair a
+	/// [`Length::fluid`] width with a fluid font size so box and glyphs
+	/// scale together. Without this the field claims `max_width`.
+	pub fn fixed_width( mut self, w: impl Into<Length> ) -> Self
 	{
-		self.fixed_width = Some( w );
+		self.fixed_width = Some( w.into() );
 		self
 	}
 
@@ -442,7 +444,7 @@ impl<Msg: Clone> TextEdit<Msg>
 			( max_width, h )
 		} else {
 			let w = self.fixed_width
-				.map( |fw| fw.min( max_width ) )
+				.map( |l| l.resolve( canvas.viewport_layout(), Length::EM_BASE_DEFAULT ).min( max_width ) )
 				.unwrap_or( max_width );
 			let h = self.height
 				.map( |l| l.resolve( canvas.viewport_layout(), Length::EM_BASE_DEFAULT ) )