Menus: Add bulk moving to selected menu items

[Sukhendu2002]

Trac ticket: https://core.trac.wordpress.org/ticket/51964

The classic Appearance → Menus screen currently allows administrators to bulk-remove menu items, but not bulk-move them. Moving several items through the existing individual parent and position controls is inefficient, especially for larger menus.

This PR adds bulk controls for choosing:

• A destination parent.
• A starting position under that parent.
• An action to move the selected items.

Manual testing steps

Setup

1. Activate a classic theme that supports Appearance → Menus.

2. Open Appearance → Menus.

3. Create or select a menu containing several root items and nested descendants.

4. Use a structure similar to:

   Home
   Products
     Product A
       Documentation
   About
     Team
   Contact
   Sample Page
   

Basic bulk movement

1. Enable Bulk Select.
2. Select two non-adjacent root items, such as Products and Contact.
3. Confirm that the Menu Parent control becomes enabled.
4. Select About as the parent.
5. Confirm that Starting Position becomes enabled.
6. Select a starting position.
7. Activate Move Selected Items.
8. Confirm that:
   • The selected roots appear under About.
   • They are placed contiguously.
   • Their relative order is unchanged.
   • Products retains its complete descendant subtree.
   • Existing children of About remain in the expected order.

Selected parent and descendant

1. Reload or restore the original menu structure.
2. Enable Bulk Select.
3. Select Products, Product A, and another root such as Contact.
4. Move the selection under About.
5. Confirm that Product A is not moved twice.
6. Confirm that the complete Products subtree remains intact.

Keyboard and accessibility

1. Navigate to Bulk Select using only the keyboard.
2. Select menu items using the keyboard.
3. Tab through Menu Parent, Starting Position, and Move Selected Items.
4. Confirm that controls are disabled until their required preceding choices are complete.
5. Activate the move using the keyboard.
6. With a screen reader, confirm that the number of moved menu items is announced.
7. Confirm that a rejected destination produces an assertive failure announcement and returns focus to Menu Parent.

Screenshots

Parent choices exclude selected subtrees

Selected subtrees moved under About

Use of AI Tools

AI assistance: Yes
Tool(s): Pi coding agent
Model(s): GPT-5.6
Used for: Initial code skeleton, test suggestions, code review, PR description drafting; final implementation and tests were reviewed and edited by me.

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