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]>

src/data/vesselLabels.test.mjs

@@ -29,6 +29,8 @@ test('normalizeVesselType preserves text and degrades unknown codes', () => {
   assert.equal(normalizeVesselType('Crude Oil Tanker'), 'Crude Oil Tanker');
   assert.equal(normalizeVesselType('0'), '');
   assert.equal(normalizeVesselType('25'), 'OTHER');
+  assert.equal(normalizeVesselType('100'), '');
+  assert.equal(normalizeVesselType('255'), '');
   assert.equal(normalizeVesselType(undefined), '');
 });