test: take only an approval window whose approval is still pending (closes #287)

The site-connection tests settle the prompt in a tab while the toolbar
popup for the same approval is still loading. Closing the tab tears that
popup down, chrome.action.openPopup() rejects, and the background opens
its fallback window for the settled approval and removes it again. The
next test took any page at an approval URL, so it could take that
window, which showed the site view and then closed under the wait for
the sign view. The harness now asks the background whether a page's
approval is still pending before taking it.

The blocklist test clicked its self-closing Reject with a plain click;
it now clicks it as the other site Reject does, with the click witnessed.

Model: opus-5-5

README.md

@@ -619,14 +619,13 @@ The jobs **report, they do not gate.** A failure is a red mark against the
 commit that a reviewer has to account for, not a hard block: whether a check
 blocks a merge is Gitea branch protection, which this repo does not configure.
 
-That is not only a statement about configuration. The Chrome suite is
-**measurably flaky under load** — two of six runs of unmutated code on a busy
-machine lost the approval popup out from under the dApp signing wait, always in
-the `#183` section, tracked as
-[#287](https://git.eeqj.de/sneak/AutistMask/issues/287). So a red `e2e-chrome`
-has to be read before it is believed, and that flake is the blocker to ever
-making this a required check. Do not answer it with a retry wrapper: a suite
-that reruns until it is green stops being evidence.
+That is not only a statement about configuration. One report of the Chrome suite
+**failing under load** is still open:
+[#290](https://git.eeqj.de/sneak/AutistMask/issues/290) records runs on a busy
+machine failing with `the extension opened no approval window within 30000ms`.
+So a red `e2e-chrome` has to be read before it is believed, and that report is
+the blocker to ever making this a required check. Do not answer it with a retry
+wrapper: a suite that reruns until it is green stops being evidence.
 
 Nothing in either job can pass vacuously. There is no `continue-on-error` and no
 `|| true`; both scripts exit non-zero when docker is missing, when the image