issue 4531 slice 41: PublishingShell unapprove one incremental queue item #4913

Parent: #4531

Slice goal

On PublishingShell, an operator removes approval from one incremental-queue item that is currently approved. Confirm reloads the list. Cancel writes nothing.

Out of scope

Approving an item (separate slice). Clearing the queue. Deleting the content item.

Acceptance criteria

• Unapprove confirm clears approval for that item only. Cancel does not write.
• 400/403/404 stay on the panel.
• Playwright surface spec + product-docs publishing note.
• Update parent [8.2] Unified publishing — next React increments #4531 Agent progress.

Change class

One vertical increment.

Leave unassigned. Do not add In Progress.

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