feat(flights): publish verticalRateMps on the tracked-aircraft descriptor

`mapAnalystRecord` has always published `verticalRateMps`, but the tracked
seam — `getTrackedInfo()` / `getTrackedSubject()`, built by `_describeFlight`
— did not, so anything needing climb/descent had to reach past the public
descriptor into the raw poll record.

Both layers now map it, which matters because they store it under different
keys: the civil records write `verticalRate` (records.js), the military ones
write `verticalRateMps`. Mapping only one would leave
`resolveTrackedAircraftInfo()` handing back two different shapes, and a
consumer reading the field off a civil contact would silently read every
military contact as level flight.

Reported, never derived. `stickyNumber` seeds the field with null, so an
aircraft that has not transmitted a rate publishes null rather than a
level-flight 0 — absent is not level, and a flight-phase classifier that
cannot tell them apart calls a climbing aircraft cruise.

Tests: both layers, both halves (a reported rate arrives with its sign; an
absent one stays null). Mutation-verified — removing either field or
defaulting it to 0 turns them red.

`docs/CURRENT-STATE.md` records the descriptor field, the two record keys it
reconciles, and the reported-never-derived rule.

CHANGELOG.md

@@ -77,6 +77,11 @@
   Native point, billboard and label highlighting uses GPU draw commands; there
   is no scene-dimming effect selector. Unsupported shaders retain native contact
   rendering, and leaving Cyber restores the standard shell and contact treatment.
+- The tracked-aircraft descriptor now publishes `verticalRateMps`, on both the
+  civil and military layers, so a consumer reading `getTrackedInfo()` no longer
+  has to reach past it into the raw poll record for climb/descent. Reported,
+  never derived: an aircraft that has not transmitted a rate reads as `null`
+  rather than a level-flight `0`.
 
 - Add a **Recent Imagery** data layer (NASA GIBS · HLS + VIIRS, keyless).
   Select a box (drag, the current view, or around a pin; up to 1,000 km a