A right-click on a photo (or any widget) while its own context menu was open
flashed the menu at the new spot and closed it again on the same frame. egui's
`Popup::show` judges "was open last frame" by the popup's id, so the click that
reopened the menu at the pointer also counted as a click while open and closed
it under `CloseOnClick`. A right-click on a different widget was fine.
`widgets::context_menu` wraps `Popup::context_menu` and ignores clicks on the
frame of the right-click that opens or moves the menu; every context menu
(30 sites) goes through it, and `TextField` applies the same rule to its
close-on-click-outside menu (`widgets::context_menu_close`).
Tests: `right_clicking_elsewhere_moves_the_context_menu` (headless grid; failed
at the second frame before the fix) and `right_clicking_again_moves_the_menu`
(text field). docs/ui-parity.md: Context menus row and revision history.
Fixes#1877
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
