fix: closing a transaction or signature approval window leaves the request pending (closes #673)

The browser can close the approval window when the user clicks away from it,
for example to copy the password from a password manager. Closing it used to
reject the request with 4001. Now the request stays pending and the site gets
no answer. Until it is answered, the toolbar popup opens the oldest such
approval.

Reject now closes its window only after the background has the rejection. Sent
as the window closed, the rejection could be lost, which the old window-close
rejection hid.

Site-connection and network-switch windows still reject the request when
closed.

Model: opus-5-5

docs/README.md

@@ -306,6 +306,13 @@ enter your password and click "Confirm" to authorize it. Message and typed-data
 signature requests work the same way, with a "Sign" button, and also require
 your password.
 
+If a transaction or signature popup closes before you answer, for example when
+you click away to copy your password, the request stays open. Closing the popup
+does not turn the request down. Click the AutistMask icon in your browser
+toolbar to bring the request back. Until you answer, the icon opens the request
+instead of your wallet. If several requests are waiting this way, the oldest
+comes first.
+
 A connected site can also ask to switch the wallet's network. A popup shows the
 site's origin, the current network and the requested network. Nothing changes
 unless you click "Switch"; clicking "Reject" or closing the popup leaves