Mark the row a heading or separator spans

Core pads that cell `15px 10px` while padding the label cell
`20px 10px 20px 0`, so a label starts at the table's edge and the spanning
cell starts ten pixels in — every divider sat indented relative to everything
it divided.

All three libraries that build this row had their own wrapper class, so a rule
keying on any one of them would have fixed a third of it. They share one now,
and the rule lives with the stylesheet in the kit.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tk8y5eZa3CHVVSM6nVxsJw

Author: arraypress

src/SettingFields.php

@@ -677,7 +677,7 @@ private function render_table( FieldSet $set, array $fields ): void {
 			// one control beside one label.
 			if ( $type->spans_row() ) {
 				printf(
-					'<tr class="field-kit__settings-row"><td colspan="2">%s</td></tr>',
+					'<tr class="field-kit__settings-row field-kit__spans-row"><td colspan="2">%s</td></tr>',
 					$set->render_field( $field, '', false ) // phpcs:ignore WordPress.Security.EscapeOutput.OutputNotEscaped -- the kit escapes as it builds.
 				);