iOS 26: Fix buttons in Editor

[kean]

Fixes https://linear.app/a8c/issue/CMM-473/fix-the-back-button-in-the-gbk-based-editor.

• Simplifies the close button – just show the "xmark" (standard behavior).
• Fixes the missing padding in the "Publish" button
• Show other controls in a single group.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	28679
	Version	PR #24779
	Bundle ID	org.wordpress.alpha
	Commit	3264478
	Installation URL	6ak80e1rsifgo

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	28679
	Version	PR #24779
	Bundle ID	com.jetpack.alpha
	Commit	3264478
	Installation URL	4390gno280s7g

Automatticians: You can use our internal self-serve MC tool to give yourself access to those builds if needed.