test(firms): cover both coordinate bounds and blank values on each axis

Documents the adapter's skip rule and cross-references the two checks, which
sit in separate packages (provider parser and fire layer).

src/data/firmsAdapt.js

@@ -7,8 +7,8 @@
  */
 
 /**
- * Map proxy fire records into internal fire records. Records with
- * non-finite coordinates are skipped; `index` is the post-skip position
+ * Map proxy fire records into internal fire records. Records with missing,
+ * non-numeric or out-of-range (WGS84) coordinates are skipped; `index` is the post-skip position
  * (it keys pick ids and context-store ids, so it must stay sequential).
  * `contextEntity`/`position` start null and are lazily filled by the layer.
  * @param {?Array<Object>} records - /api/firms `fires` array.
@@ -119,6 +119,7 @@ function finiteNumber(value) {
   return Number.isFinite(number) ? number : 0;
 }
 
+// Same rule as parseFirmsCsv: a blank or non-numeric value is not a zero.
 function hasCoordinateValue(value) {
   return (
     typeof value === 'number' ||