fix(tools): average aircraft speed over airborne aircraft only

aircraft_in_area stats summarized altitude over airborne aircraft but
speed over every match, so parked aircraft pulled the mean speed toward
zero. Both figures now use the same airborne subset, and the on-ground
fixture is stationary so the test can tell the difference.

Reserved AIS ship-type codes 100 to 255 now read as unknown, as type 0
does, instead of showing up in the breakdown as their own type.

Adds tests for an area where every aircraft is on the ground and for
find_vessel type and destination normalization, and notes in the
changelog fragment that every vessel answer is now normalized.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

changelog.d/1056-area-tool-breakdowns.md

@@ -5,5 +5,8 @@
   in each callsign (SWA1234 counts as SWA), so the breakdown works on feeds
   that report no operator; operator and type are counted only where the feed
   reports them. Ship types count by family, so AIS codes 70 to 79 are all
-  cargo, and type 0 ("not available") counts as unknown
-  (quanticsoul4772, #1056).
+  cargo; type 0 ("not available") and the reserved codes 100 to 255 count as
+  unknown. Altitude and speed stats cover airborne aircraft only, so parked
+  aircraft do not pull the means down. Every vessel answer, `find_vessel`
+  included, now reads AIS ship-type codes as their family and a destination
+  with no letters as unknown (quanticsoul4772, #1056).