layout: adaptive grid and vertical flex; enforce the mechanical style rules

grid_min_cell( width ) adds the adaptive mode WrapGrid was missing: instead of a fixed column count, the count is derived at layout time from the available width so every cell is at least `width` wide (any Length, so a fluid threshold works; never fewer than one column), re-derived on every resize. Cells then share the width equally, and WrapGrid::max_columns( n ) caps the derived count so cells grow instead of multiplying on very wide surfaces — the cap only applies to the adaptive mode, grid( n ) keeps the fixed behaviour untouched. Four new layout tests cover width derivation, spacing accounting, the one-column floor and the cap; the row-wrap assertions check X positions rather than Y because zero-height spacer children produce zero-height rows.
flex( child ) now distributes leftover height inside a Column, mirroring its leftover-width behaviour in a Row: flex children join the weight pool alongside weight-only spacers and y-scrolls, draw their child inside the allocated share at full inner width, and contribute zero to the column's natural height exactly like a row counts flex width. This closes the documented "vertical flex is not yet implemented" gap; the Flex rustdoc and the widgets.md entry now describe both axes.
Add scripts/style-check.sh and a make stylecheck target, wired into CI: mechanical verification of the grep-checkable subset of code_style_guide.md — tab indentation and spaces inside attribute brackets — with comment lines skipped so prose may cite raw attribute syntax. To turn the check on green, the 82 unspaced attribute sites across 24 files (#[test], #[derive(...)], #[cfg(...)], #[allow(...)]) were normalized to the spaced form. CONTRIBUTING and the style guide reference the new target; brace placement and paren spacing remain review concerns.

src/widget/carousel/mod.rs

@@ -26,7 +26,7 @@ use crate::render::Canvas;
 use crate::types::{ Rect, WidgetId };
 use crate::widget::Element;
 
-#[cfg(test)]
+#[ cfg( test ) ]
 mod tests;
 
 pub struct Carousel<Msg: Clone>

src/widget/carousel/tests.rs

@@ -17,7 +17,7 @@ fn three_spacer_carousel() -> Carousel<()>
 		.push( spacer() )
 }
 
-#[test]
+#[ test ]
 fn empty_layout_is_empty()
 {
 	let c: Carousel<()> = carousel();
@@ -25,7 +25,7 @@ fn empty_layout_is_empty()
 	assert!( c.layout( rect, &canvas() ).is_empty() );
 }
 
-#[test]
+#[ test ]
 fn first_child_centred_at_offset_zero()
 {
 	let c = three_spacer_carousel();
@@ -36,7 +36,7 @@ fn first_child_centred_at_offset_zero()
 	assert!( ( rects[0].0.width - 80.0 ).abs() < 0.01 );
 }
 
-#[test]
+#[ test ]
 fn children_strided_by_child_width_plus_gap()
 {
 	let c = carousel::<()>()
@@ -50,7 +50,7 @@ fn children_strided_by_child_width_plus_gap()
 	assert!( ( rects[1].0.x - ( rects[0].0.x + 108.0 ) ).abs() < 0.01 );
 }
 
-#[test]
+#[ test ]
 fn snap_offset_centres_target_index()
 {
 	let c = three_spacer_carousel();
@@ -58,7 +58,7 @@ fn snap_offset_centres_target_index()
 	assert!( ( c.snap_offset( 100.0, 2 ) - ( -160.0 ) ).abs() < 0.01 );
 }
 
-#[test]
+#[ test ]
 fn focused_index_rounds_to_nearest_tile()
 {
 	let mut c = three_spacer_carousel();
@@ -68,7 +68,7 @@ fn focused_index_rounds_to_nearest_tile()
 	assert_eq!( c.focused_index( 100.0 ), 1 );
 }
 
-#[test]
+#[ test ]
 fn focused_index_clamps_to_valid_range()
 {
 	let mut c = three_spacer_carousel();
@@ -78,7 +78,7 @@ fn focused_index_clamps_to_valid_range()
 	assert_eq!( c.focused_index( 100.0 ), 2 );
 }
 
-#[test]
+#[ test ]
 fn offset_shifts_all_children_horizontally()
 {
 	let c = three_spacer_carousel().offset( -25.0 );
@@ -90,7 +90,7 @@ fn offset_shifts_all_children_horizontally()
 	assert!( ( rects[1].0.x - rects[0].0.x - 80.0 ).abs() < 0.01 );
 }
 
-#[test]
+#[ test ]
 fn focused_width_frac_is_clamped_to_unit_range()
 {
 	let c: Carousel<()> = carousel().focused_width_frac( 5.0 ).push( spacer() );
@@ -99,7 +99,7 @@ fn focused_width_frac_is_clamped_to_unit_range()
 	assert!( c2.focused_width_frac > 0.0 );
 }
 
-#[test]
+#[ test ]
 fn children_use_full_rect_height()
 {
 	let c = three_spacer_carousel();