fix(search): normalize geocoder bias across the antimeridian (#1272)

Keep geocoder viewport bias near the antimeridian and omit misleading wrapped viewboxes.

Contribution by @asturksever.

docs/CURRENT-STATE.md

@@ -5197,9 +5197,14 @@ HTTP refusals and outages remain retryable. Searches share a 12-second total
 deadline, with Photon requests capped at six seconds each. Caller/application
 cancellation stops retries and late cache writes. Replacing a location search
 cancels the previous lookup; disposing its controls cancels the active lookup. Photon uses a soft proximity bias, up to five
-candidates, and an unbiased retry for name mismatches. Invalid/wrapped bounds
+candidates, and an unbiased retry for name mismatches. Invalid or wrapped bounds returned by providers
 are omitted rather than framing the wrong part of the globe.
 
+For request viewport bias, Photon unwraps antimeridian-crossing longitude bounds
+before computing their midpoint, then wraps that midpoint back into ±180 degrees.
+Malformed viewport bounds add no proximity bias. Nominatim omits a crossing
+request viewbox and continues searching without that geographic preference.
+
 ### Map Stack Switcher (June 2026)
 
 - `src/mapStackController.js` switches between Google Photorealistic 3D (`photoreal`, the default when a Google or ion key is present), keyless Esri World Imagery (the zero-key default landing, with keyless terrain), Bing Aerial / Aerial-with-Labels via Cesium ion world imagery (require `CESIUM_ION_TOKEN`), and OSM tile fallback. Bing Road is **retired**: it is gone from `MAP_STACKS`, from the `set_map_stack` enum, and from the voice aliases (road phrasings now resolve to OSM, the one shipped road basemap). An old `map=bing-road` link is simply an unknown id and takes `setStack()`'s existing photoreal fallback with the Google 3D tile lit — pinned live in `scripts/qa-map-source-tray.mjs`.