Empty gray theme-actions div on Appearance > Themes for classic themes with no customizer support

[awetz583]

If a Classic/Hybrid theme that has the Customizer disabled is active in the Appearance > Themes screen, there is a stray gray box in the bottom right corner of theme's box.

This appears to be because there is an empty div <div class="theme-actions"> </div> that has corresponding CSS to add a gray background and some padding.

For most themes, there is a Customize button there. It would be great if this div was removed or they styles were changed if it was empty of buttons.

I can see this issue in 6.9, but it is much more noticeable in 7.0 Beta 1 because the background color for the active h2.theme-name has been changed from dark gray #1d2327 to bright blue #3858e9

[awetz583]

Bottom of an active classic theme that does not have a customize button

Changes the active theme actions panel to have no background color to avoid possibility of empty background.

Trac ticket: https://core.trac.wordpress.org/ticket/64720

## Use of AI Tools

After change:

With customizer disabled:

Before, with customizer enabled:

It looks good after this PR, but I still notice a very minor box-shadow when the Customizer is disabled.

[noruzzaman]

Test Report

Patch tested: ​https://github.com/WordPress/wordpress-develop/pull/11121

Environment

• WordPress: 7.0-beta2-61809
• PHP: 8.3.30
• Server: PHP.wasm
• Database: WP_SQLite_Driver (Server: 8.0.38 / Client: 3.51.0)
• Browser: Chrome 145.0.0.0
• OS: macOS
• Theme: Twenty Fourteen 4.4
• MU Plugins: None activated
• Plugins:
  • Disable Customizer 2.2.7
  • Test Reports 1.2.1

Actual Results

1. ✅ The primary issue addressed by the patch is resolved.

2. ⚠️ A minor visual issue still remains.

The .theme-actions container still renders a small box-shadow (inset 0 1px 0 rgba(0,0,0,0.1)), which creates a thin visual line in the active theme bar.

Before	After

The PR works as expected; we just need to address the box-shadow issue when customizer disable.

|Before|After|After with Customizer Button

| ||

I removed the box-shadow on the active theme actions container. It was pretty much entirely invisible when the customizer was active, so the only case where you could really see it was this one.

[joedolson]

In 61831:

Themes: Remove background on active theme actions.

The background behind theme actions for the active theme was still visible when no actions were available, such as with a disabled customizer. Removing the background on this container improves the design of the active theme card by simplifying the layout and prevents the appearance of an error if no actions are available.

Remove background and inset box shadow for the .theme.active .theme-actions container on the active theme.

Props awetz583, huzaifaalmesbah, noruzzaman, shailu25, joedolson.
Fixes #64720.