Run a trailing hover check for the last suppressed pointer position

A move inside the 120 ms hover throttle window was dropped, so a pointer
that stopped right after a pick kept a stale cursor (pointer over empty
space, or default over a mission) until the next move. Keep a copy of the
last suppressed position (Cesium reuses the movement object) and run one
trailing check when the window ends. The check rechecks hover eligibility
and is cancelled by reset, disable, camera motion, and destroy.

Tests cover a stopped pointer in both directions without another event,
the copied position, one timer at a time, cancellation, and the
eligibility recheck.

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

changelog.d/1279-launch-issue-fix.md

@@ -1 +1 @@
-- Throttle hover picks and clear stale cursors (asturksever, #1279).
+- Throttle mission hover picks with a trailing check for the last pointer position, and clear stale cursors (asturksever, #1279).