harden: one connection and one signature prompt per site at a time (closes #405)

Each eth_requestAccounts or personal_sign call opened another approval
window, so a page calling in a loop could cover the screen with identical
prompts. While a site's connection or signature prompt is unanswered, a
further request of that kind from the same site is now refused with
EIP-1193 -32002 and opens no window; all signing methods count as one
kind. A connection prompt whose toolbar popup closed before it connected,
and which the toolbar popup no longer opens, is shown again by the site's
next request instead of refusing the site until the address changes.

Model: opus-5-5

TODO.md

@@ -45,6 +45,18 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-04: A site has at most one connection prompt and one signature prompt
+  open at a time ([#405](https://git.eeqj.de/sneak/AutistMask/issues/405)). Each
+  `eth_requestAccounts` or `personal_sign` call opened another approval window,
+  so a page calling in a loop could cover the screen with identical prompts. A
+  further request of the same kind from a site whose prompt is still unanswered
+  is now refused with EIP-1193 `-32002`, the code a second transaction already
+  gets, and opens no window. Signing by `personal_sign`, `eth_sign` and
+  `eth_signTypedData_v4` counts as one kind. Other sites are not affected, and
+  the site may ask again once the user has answered. A connection prompt whose
+  toolbar popup closed before it connected, and which nothing shows any more, is
+  shown again when the site asks again.
+
 - 2026-10-04: A nonce the site supplies with `eth_sendTransaction` is ignored
   ([#404](https://git.eeqj.de/sneak/AutistMask/issues/404)). It was passed on to
   the transaction, so a site could replace one of the user's pending