Use stable Y-coordinate for character highlight and adjust height

Anchor rectangle to bounds.y for consistent vertical placement across DPI/zoom, avoid using bounds.height to calculate Y, and increase height by 1px for proper border spacing.

Author: ShahzaibIbrahim

bundles/org.eclipse.jface.text/src/org/eclipse/jface/text/source/MatchingCharacterPainter.java

@@ -267,7 +267,7 @@ private void draw(final GC gc, final int offset) {
 			final int height= fTextWidget.getCaret().getSize().y;
 
 			// draw box around line segment
-			gc.drawRectangle(bounds.x, bounds.y + bounds.height - height, width, height - 1);
+			gc.drawRectangle(bounds.x, bounds.y, width, height + 1);
 		} else {
 			fTextWidget.redrawRange(offset, 1, true);
 		}