event_loop, text_edit, layout: focus-time cursor as an end-of-value sentinel, caret height tied to the text line, row align_top/fill_height modes

Focus-time cursor (event_loop/focus.rs): focusing a text input pinned the cursor to a concrete `value.len()` snapshot. When the value keeps growing after focus without the widget seeing keystrokes — crustace's launcher search field is fed over IPC while forge routes the type-to-search keys around Wayland — that snapshot goes stale, and the first key delivered normally afterwards inserts mid-string. The cursor is now seeded with the `usize::MAX` sentinel ("end of whatever value is rendered"), the same convention `select_on_focus` fields already rely on; every consumer (insert/delete, arrow keys, draw, hit-test, context-menu paste offset, a11y tree) clamps via `cursor.min( value.len() )`, so the cursor tracks external growth and collapses to a concrete position on the first real keystroke or click. Click placement is untouched — the pointer path writes its own hit-tested offset.
Caret height (widget/text_edit/draw.rs): the single-line caret spanned `rect.height - 16`, so a field taller than its text line (the launcher's borderless search pill) grew a caret about twice the glyph height. It now measures `font_size + 4`, vertically centered like the text — matching what the multiline caret already did.
Row alignment modes (layout/row.rs): `Row` gains `align_top()` (children pinned to the top edge instead of the default vertical centering) and `fill_height()` (every non-spacer child stretched to the row's inner height, the row itself still sized by its tallest child). Both exist for siblings whose natural heights differ by a few font-metric pixels — like the QS media card next to the wifi/bluetooth chip column — where equal-height layouts cannot be achieved by estimating text heights: `new_line_size` is font-dependent, so px arithmetic in the app always drifts. Containers paint their chrome over the full rect they receive and columns absorb the extra in weighted spacers, so a stretched card keeps its content anchored where its internal spacers put it.

src/layout/row.rs

@@ -47,6 +47,8 @@ pub struct Row<Msg: Clone>
 	/// Padding on all sides. [`Length`]; default `0.0` px.
 	pub( crate ) padding:     Length,
 	pub( crate ) align_right: bool,
+	pub( crate ) align_top:   bool,
+	pub( crate ) fill_height: bool,
 }
 
 impl<Msg: Clone> Row<Msg>
@@ -59,6 +61,8 @@ impl<Msg: Clone> Row<Msg>
 			spacing:     Length::px( 8.0 ),
 			padding:     Length::px( 0.0 ),
 			align_right: false,
+			align_top:   false,
+			fill_height: false,
 		}
 	}
 
@@ -104,6 +108,26 @@ impl<Msg: Clone> Row<Msg>
 		self
 	}
 
+	/// Pin children to the top edge instead of the default vertical
+	/// centering, so siblings of slightly different heights (e.g. two
+	/// cards whose text metrics differ) share the same top line.
+	pub fn align_top( mut self ) -> Self
+	{
+		self.align_top = true;
+		self
+	}
+
+	/// Stretch every child to the row's inner height, so siblings share
+	/// both the top and the bottom line regardless of their natural
+	/// heights. The row's own height still comes from the tallest
+	/// child's preferred size; children whose content should track the
+	/// stretch need internal flexible spacers.
+	pub fn fill_height( mut self ) -> Self
+	{
+		self.fill_height = true;
+		self
+	}
+
 	/// Return the preferred `(width, height)` given available `max_width`.
 	pub fn preferred_size( &self, max_width: f32, canvas: &Canvas ) -> (f32, f32)
 	{
@@ -240,8 +264,15 @@ impl<Msg: Clone> Row<Msg>
 				Element::Flex( f )   => flex_unit * f.weight as f32,
 				_                    => w,
 			};
-			let y = rect.y + pad + ( inner_h - h ) / 2.0;
-			result.push( ( Rect { x, y, width, height: h }, i ) );
+			let ( y, height ) = if self.fill_height && !matches!( child, Element::Spacer( _ ) )
+			{
+				( rect.y + pad, inner_h )
+			} else if self.align_top {
+				( rect.y + pad, h )
+			} else {
+				( rect.y + pad + ( inner_h - h ) / 2.0, h )
+			};
+			result.push( ( Rect { x, y, width, height }, i ) );
 			x += width + spacing;
 		}
 		result
@@ -258,6 +289,8 @@ impl<Msg: Clone> Row<Msg>
 			spacing:     self.spacing,
 			padding:     self.padding,
 			align_right: self.align_right,
+			align_top:   self.align_top,
+			fill_height: self.fill_height,
 		}
 	}
 }