- Sandbox via unique app/org names plus Linux-only XDG redirection, derive
the warm-cache probe and data path from SettingsCache, and bail out when the
temporary sandbox cannot be created.
- Run each pass with a fresh worker and shut workers down before reading the
429 counters, so the redirect cache is persisted and no worker thread can
outlive the stack-local counters or the installed message handler.
- Make s_activeCounters atomic and always forward log output when the previous
handler is the built-in (nullptr) one.
- Validate --timeout-min, scale the cached-pass budget with --count, honour the
first --url as the stress template, and add the missing trailing newlines.
- Zero-initialise SettingsCache members so the benchmark mock cannot
dereference an indeterminate pointer.
