fix: open an approval window while another one has focus (closes #290)

The background centred each approval window on the last focused window,
which could be an earlier approval window still open; headless Chrome
reports one as 1280x720, the browser refused the resulting position, and
the request failed with no window. It now centres only on a browser
window, and when the browser refuses a position it asks again without one.

In the Chrome suite a test could raise its prompt while the previous
test's window was still closing. After a passed test the runner now gives
approval windows five seconds to close and fails the test if one is still
open; after a failed test it closes them.

Model: opus-5-5

TODO.md

@@ -45,6 +45,20 @@ but the review is broader than any of them.
 
 # Completed Steps
 
+- 2026-10-05: A prompt raised while another approval window has focus opens a
+  window of its own ([#290](https://git.eeqj.de/sneak/AutistMask/issues/290)).
+  The background centred each approval window on the last focused window, which
+  could be an earlier approval window still open; headless Chrome reports one as
+  1280x720, so the new window came out where the browser refused to create it,
+  and the request failed with no window at all. It now centres only on a browser
+  window, and when the browser refuses the position it asks again without one
+  and lets the browser place the window. In the Chrome end-to-end suite a test
+  could raise its prompt while the previous test's window was still closing, and
+  then either hit that refusal or take the closing window for its own. After a
+  test that passed, the runner now waits a few seconds for approval windows to
+  close and fails the test if one is still open; after a test that failed, it
+  closes them.
+
 - 2026-10-05: The Send screen has a "Max" button
   ([#198](https://git.eeqj.de/sneak/AutistMask/issues/198)). Emptying an ETH
   address took guessing an amount and being refused by the confirmation screen's