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.

docs/CURRENT-STATE.md

@@ -3222,6 +3222,7 @@ its criteria cannot be silently ignored.
 | Live AIS Vessels 🚢    | AISStream websocket                                                                                                                                                                             | `src/data/aisLiveVessels.js`                          | `/api/vessels`                                          | 60s (+800ms visibility pass)                                                      |
 | Mapped Installations ⌖ | OpenFreeMap military areas; optional configured Overpass names and Google Places search | `src/data/militaryInstallations.js` | OpenFreeMap tiles, `/api/military-installations`, `/api/google/text-search` | viewport-driven; transient errors back off, missing capability switches to tiles |
 | Earthquakes            | USGS                                                                                                                                                                                            | `src/data/earthquakes.js`                             | —                                                        | 60s                                                                               |
+| Air quality            | ECCC MSC GeoMet OGC API (AQHI, Canada only)                                                                                                                                                      | `src/layers/airQuality/`                              | —                                                        | 20 min readings, 12 h station catalog                                             |
 | Satellites             | CelesTrak                                                                                                                                                                                       | `src/data/satellites.js`                              | `/api/celestrak`                                         | 120s                                                                              |
 | Space Missions (30d)   | Launch Library 2 + CelesTrak                                                                                                                                                                    | `src/data/rocketLaunches.js`                          | `/api/launches` + `/api/celestrak/active`                | 5 min                                                                             |
 | Traffic | Selectable TomTom / OpenStreetMap / Hybrid roads; optional TomTom flow (BYOK) | `src/data/traffic.js` | browser-direct OpenFreeMap tiles; `/api/tomtom` for flow | viewport-driven; capped tile cache |