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.

docs/CURRENT-STATE.md

@@ -567,6 +567,13 @@ use the supplied asset resolver, including the preload path. Enrichment receives
 an abort signal and cannot update a later lifecycle after destruction. Existing
 camera, terrain floor, trail, selection and measured model-size policies remain.
 
+The tracked-aircraft descriptor both flight layers hand to the cockpit carries
+`verticalRateMps` beside `velocityMps` and `track`. Civil records store the rate as
+`verticalRate` and military records as `verticalRateMps`; the query seam maps both to
+one name, so `resolveTrackedAircraftInfo` returns a single shape for either layer. The
+rate is reported, never derived: a blank poll keeps the last transmitted value and an
+absent rate stays null rather than reading as level flight.
+
 ## Browser live-source observations
 
 Flights, Military Flights and AIS Vessels obtain snapshots and optional history