window.confirm/alert render as chrome-owned, Theseus-branded OS boxes
outside the sidebar, which breaks the illusion that Aegis is one
coherent surface — and they can't carry an icon, a danger-styled
button, or formatted copy.
Adds aegisConfirm() / aegisAlert(): the same overlay shell the manage
and import modals already use, resolving like confirm() so callers
just await it. Escape cancels, Enter confirms, click-outside cancels.
Swapped at all four confirm sites (remove wallet from the picker,
remove wallet from Settings, remove PIN, sign out) and all seven
alert sites.