alert / confirm / prompt from a page came up as bare OS message boxes
titled "theseus-navigator" (the package name), with no hint of who was
asking and nothing of the browser's styling — the PDF Editor's "Delete
signature?" was the reported case.
The session preload replaces the page's three functions with wrappers
that hand the call to the isolated world through a DOM event, which
asks main synchronously and writes the answer back; pages see Chrome's
return values (confirm → boolean, prompt → string or null) and no new
global. Main answers from a sheet hanging under the toolbar, in the
same surface as add-on approvals, that names who is asking: the site's
host, the add-on's name for an add-on page or panel (identified by its
path under the profile's extensions directory), or Theseus for its own
pages. The sheet belongs to the tab that asked — hidden while another
tab is in front, back when its tab returns — and a closing tab or
window answers "cancel" so no renderer stays blocked. Windows without
the chrome (installed apps, plain windows) get a native box with a
proper title, and app.name now reads "Theseus Navigator" for whatever
else still shows one.
