Summary of the Pull Request

Fixes the context menu crash reported in #20570 after interacting with the Split pane submenu and collapsing/re-expanding the root menu.

This replaces the nested CommandBarFlyout child menus with standard MenuFlyout controls.

References and Relevant Issues

Closes #20570

Related: #20332

The repro from #20332 also no longer occurs on the patched build.

Detailed Description of the Pull Request / Additional comments

• Replaces the nested Split pane and Swap pane CommandBarFlyout menus with MenuFlyout.
• Uses MenuFlyoutSubItem for duplicate/profile split entries, with an explicit Automatic option followed by the directional split options.
• Keeps the top-level context menu as a CommandBarFlyout.
• Adds the localized Automatic label.
• Adds a structural regression test verifying the Split and Swap child flyout types.

Validation Steps Performed

• ContextMenuUsesMenuFlyoutsForSplitAndSwapPane: 1 passed, 0 failed.
• Full TabTests: 22 passed, 0 failed, 0 blocked, 0 skipped.
• CascadiaPackage Debug x64: built successfully (0 errors).
• CascadiaPackage Release x64: built successfully (0 errors).
• Re-tested the exact The show/hide toggle button from the context menu freezes and crashes the whole terminal (all tabs, all windows) #20570 repro manually; the crash no longer reproduces.
• Verified Automatic split, directional split, profile split, Swap pane, and dismiss/reopen behavior.
• Re-tested the context menu gets stuck when sub menu is shown #20332 repro; it no longer reproduces on the patched build.

Video

PR Checklist

• Closes The show/hide toggle button from the context menu freezes and crashes the whole terminal (all tabs, all windows) #20570
• Tests added/passed
• Documentation updated
  • If checked, please file a pull request on our docs repo and link it here: #xxx
• Schema updated (if necessary)