- Replace innerHTML = '' with replaceChildren() throughout tabs.js and
app.js (12 + 7 sites). paintAtomic already used replaceChildren; now
the direct-clear sites are consistent with it.
- Add missing .rqe-source-startup_sweep CSS rule (startup_sweep is a
valid QueueSource variant but had no badge style, falling through to
the base muted appearance with no explicit intent).
- Lowercase the one uppercase 'HTTP ' in the fetchAndRenderToolGroups
error path to match every other fetch error in the file.