fix: a slow answer to an approval still reaches the site (closes #540)

Chrome stopped the background worker about six minutes after a site's
request even with the approval window open, and the approval and the
site's waiting request went with it. While any approval is pending, the
worker now calls runtime.getPlatformInfo() every 20 seconds; Chrome
counts each extension call as activity. The timer is the worker's own,
so a minimized window does not slow it, and it stops itself once nothing
is pending.

tests/e2e/slowApproval.js, run by make test-e2e, leaves a transaction
and a signature approval open for seven minutes in minimized windows and
requires the site to receive both results. It drives Chromium over the
DevTools pipe without Playwright, because Playwright keeps DevTools
attached to the worker and Chrome then never stops it.

Model: opus-5-5

.gitea/workflows/e2e.yml

@@ -35,10 +35,10 @@ on: [push]
 jobs:
     e2e-chrome:
         runs-on: ubuntu-latest
-        # Bounds the image build, a cold cache included, and both Chrome
+        # Bounds the image build, a cold cache included, and the three Chrome
         # programs, so a hung browser frees the shared runner. README.md
         # "In CI" has the measured times.
-        timeout-minutes: 20
+        timeout-minutes: 40
         steps:
             # actions/checkout v4.2.2, 2026-02-22
             - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683