feat(globe): follow camera on both engines

camera.follow({ position, viewFrom, minRange = 150, native? }) keeps a
moving target centred at an east-north-up offset the user may turn and
zoom; camera.following() and camera.followChanged report it; stop() frees
the camera and a camera command (setView, flyTo, flyToSphere, lookAt,
cancelFlight) ends it.

Probe ruling: Navara 0.2.1's cameraFollow holds the target but ignores the
user's drag and wheel, the aircraft sits ~13 px off centre with 7.6 px of
spread, and calling it without an offset each frame gives a NaN camera.
So Navara (and the fake engine) follow with src/globe/follow.js: each
frame, before Navara draws, the offset is re-read from where the user put
the camera relative to the previous target, kept outside the minimum
range and carried to the new target.

Cesium follows with viewer.trackedEntity: the layer's own Entity
(`native`) or a proxy Entity at position() with a 1 px transparent point,
since EntityView moves the camera only for an entity with a bounding
sphere. applyTrackedCameraFrame and the zoom limits moved to
src/globe/cesium/follow.js; src/data/trackedCamera.js keeps the pure parts
(the range clamp now lives in src/globe/follow.js). following() also
reports an entity the app tracked itself. Camera sensitivity claims made
on a viewer's Cesium camera now share the engine camera's ledger, and the
orientation controls and the world jump read the follow from the engine.

Contract (both engines): a target flying at 250 m/s stays within 3 px of
the centre for 2 s, zoomIn through it stops at 150 m, stop() and setView
end the follow. Cesium 71/71, Navara 77/77; shell 23/25/4.

scripts/package-boundaries.json

@@ -1220,7 +1220,9 @@
       "src/geo/scaleToGeodeticSurface.js",
       "src/geo/check.js",
       "src/geo/debug.js",
-      "src/geo/developerError.js"
+      "src/geo/developerError.js",
+      "src/globe/contract.js",
+      "src/globe/cesium/engineFromViewer.js"
     ],
     "external": ["cesium", "@mapbox/vector-tile", "pbf"]
   },
@@ -1316,7 +1318,9 @@
       "src/geo/scaleToGeodeticSurface.js",
       "src/geo/check.js",
       "src/geo/debug.js",
-      "src/geo/developerError.js"
+      "src/geo/developerError.js",
+      "src/globe/contract.js",
+      "src/globe/cesium/engineFromViewer.js"
     ],
     "external": ["cesium", "pbf", "@mapbox/vector-tile"]
   },
@@ -1353,7 +1357,9 @@
       "src/geo/scaleToGeodeticSurface.js",
       "src/geo/check.js",
       "src/geo/debug.js",
-      "src/geo/developerError.js"
+      "src/geo/developerError.js",
+      "src/globe/contract.js",
+      "src/globe/cesium/engineFromViewer.js"
     ],
     "external": ["cesium"]
   },
@@ -2542,10 +2548,12 @@
       "src/globe/pickDelivery.js",
       "src/globe/navara/clock.js",
       "src/globe/cesium/lines.js",
+      "src/globe/follow.js",
       "src/globe/lines.js",
       "src/globe/navara/movers/pickIds.js",
       "src/globe/cesium/movers.js",
       "src/globe/movers.js",
+      "src/globe/cesium/follow.js",
       "src/globe/cpuPicks.js",
       "src/globe/navara/picking.js",
       "src/globe/navara/lines/lineMesh.js",
@@ -3122,7 +3130,9 @@
       "src/geo/check.js",
       "src/geo/debug.js",
       "src/geo/developerError.js",
-      "src/time/clock.js"
+      "src/time/clock.js",
+      "src/globe/follow.js",
+      "src/globe/cesium/follow.js"
     ],
     "external": [
       "hls.js",
@@ -3735,7 +3745,9 @@
       "src/geo/scaleToGeodeticSurface.js",
       "src/geo/check.js",
       "src/geo/debug.js",
-      "src/geo/developerError.js"
+      "src/geo/developerError.js",
+      "src/globe/contract.js",
+      "src/globe/cesium/engineFromViewer.js"
     ],
     "external": ["cesium", "pbf"]
   },