Stop the strict acceptance from waiting for itself

A scenario whose body ran past about 19 s idled until 45 s after its
start, and twice one never exited and hit the runner's 300 s timeout
after it had passed: something of Chrome outlived Browser.close and kept
its stdout and stderr open.

- scripts/qa/browser.mjs closes Chrome within 5 s, kills its process
  group and closes its pipes; the harness then finishes and exits with
  the scenario's code. QA_EXIT_DIAGNOSTICS=1 keeps the old ending and
  prints the open handles and Chrome's process tree 5 s after finish.
- Every strict page starts with its clock at the 18:30 UTC nearest to
  the real time, so Navara's sun is up over the test cities whenever the
  acceptance runs; a scenario can ask for its own instant or the real
  clock (Wildlife does, for its freshness fixtures).
- The runner records a scenario that passed but did not exit as hung,
  kills the whole process group on a timeout, runs a failed scenario
  once more and reports one that passes then as flaky, and appends each
  run to --history=FILE; scripts/report-acceptance-flake.mjs reads it.

scripts/qa-navara-bloom.mjs

@@ -21,7 +21,6 @@ import {
   diff,
   freeze,
   pickStyle,
-  pinDaytime,
   saveCapture,
   stats,
   visualPageUrl,
@@ -59,7 +58,6 @@ await strict.run({}, async (browser) => {
   page.on('pageerror', (error) => errors.push(error.message));
   // The same sun on every run: the frame's brightness decides what blooms
   // and what each style's signature reads.
-  await pinDaytime(page);
   await page.evaluateOnNewDocument(() => {
     localStorage.setItem('gev:first-run-mission:v1', 'suppressed');
   });