Style States: Allow unsetting background image per viewport

[shail-mehta]

What?

Part of #80388

Allows unsetting a block background image for a specific viewport/pseudo style state (e.g. Mobile or Tablet).

Previously, clearing/resetting the background image in a viewport removed the override, so the default-state image still showed. Reset now stores backgroundImage: 'none' for that state only, and the default-state image is exposed as inherited so Remove/Reset is available.

Why?

Background image works but can't be unset for a particular viewport

Without an explicit unset value, the cascade keeps the default-state background image. Reset all could also miss viewport scoping and clear the default-state image across devices.

How?

• Merge the block's default-state background into the panel's inherited value when a style state is selected, so Remove appears.
• Persist backgroundImage: 'none' on Reset / Reset all / media Reset under a selected style state.
• Scope inspector Reset all using the selected block style state from the store, and keep full-style resets from overwriting the default-state image.
• Add unit coverage for scoped/none reset behavior.

Testing Instructions

1. Insert a Group block and set a Background → Image on the default/desktop view.
2. Go to View → Responsive styles → Mobile.
3. Open the background image control and Reset / Remove, or use Background options → Reset Image / Reset all.
4. Confirm Mobile shows no background image.
5. Switch back to the default/desktop state and confirm the original image is still there.

Use of AI Tools

• Yes

[github-actions]

Size Change: +340 B (0%)

Total Size: 7.71 MB

📦 View Changed

Filename	Size	Change
build/scripts/block-editor/index.min.js	458 kB	+340 B (+0.07%)

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[github-actions]

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Co-authored-by: shail-mehta <shailu25@git.wordpress.org>

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