Merge upstream/main: air-quality layer (AQHI) meets i18n

Upstream's #568 adds the Air quality layer to the Weather group (ECCC
AQHI, Canada only) with a band legend, worst-first list and voice
support.

- package-boundaries: both sides' entries unioned.
- layerPanel/weatherPanel tests: both sides' new tests kept; the
  weatherPanel fixture follows upstream (legendCategorical: true, the
  'list' block id) while our localized-history (K-6) test stays.
- air-quality strings marked: band labels and the provider label as
  msg() data, the readings-list aria-label through t(); es/ru entries
  added (+6 keys each).
- The synthetic air-quality allocation-benchmark titles follow the
  file's own convention (// i18n-ignore) like TRK/VESSEL/CAMERA.

Also verified the auto-merged weatherPanel.js against upstream: ORDER
gains 'air-quality', OBSERVED stays slice(2, 5), and the data-driven
legendCategorical path is upstream's.

npm run i18n: complete (2559), no unmarked strings. npm test: only the
pre-existing environmental OPENAI_API_KEY leak fails. Build passes.

src/ui/layerPanel.js

@@ -90,6 +90,7 @@ const PANEL_GROUPS = [
   {
     label: msg('Weather'),
     ids: [
+      'air-quality',
       'wind',
       'weather-radar',
       'weather-satellite',
@@ -569,6 +570,7 @@ export class LayerPanel {
               'weather-satellite',
               'weather-lightning',
               'weather-cyclones',
+              'air-quality',
             ].includes(layer.id),
         )
         .map((layer) => ({