perf(flights): skip dead-reckoning contacts that stay behind the horizon

The fleet tick dead-reckoned, floored and distance-tested every contact on
every ~80 ms tick, then hid the ones behind the horizon. The worldwide feed
carries ~13k contacts; zoomed in, well under 1% are on screen, so nearly all
of that work produced a hidden billboard.

A contact that is already hidden and still behind the horizon at its last
position now re-reckons only on its turn in a staggered one-in-12-ticks
rotation (about once a second, HIDDEN_CONTACT_DR_TICKS). Anything that
position puts in view, and any contact with a fleet model, takes the full
pass immediately, so on-screen behaviour is unchanged. Hidden-inclusive
proximity queries (getNearby includeHidden, getAllPositions) read positions
at most about a second old, well inside the 30 s poll's uncertainty.

Measured in Chrome on a Radeon 780M, ~12.9k contacts, 56 on screen over
Colombia at 4 km, same view before and after:
  fleet tick   7.66 -> 2.03 ms/frame, longest tick 50.9 -> ~16 ms
  frame        20.6 -> 14.0 ms, 42.9 -> 57.8 FPS
Teleporting the camera to Madrid showed 975 contacts within 100 ms.

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

scripts/format-scope.json

@@ -308,6 +308,7 @@
   "src/layers/flights/tracking.js",
   "src/layers/flights/rendering.js",
   "src/layers/flights/testing.js",
+  "src/layers/flights/hiddenContactRotation.test.mjs",
   "src/layers/flights/evidence.js",
   "src/layers/flights/ingestion.js",
   "src/layers/flights/queries.js",