Move satellites every frame between SGP4 samples

Satellite points were propagated once a second and held still in between,
so while the world clock plays faster than real time they jumped: at
1 min/s, about 45 px once a second at globe scale.

Each SGP4 call now keeps a sample of the satellite's inertial position,
velocity, gravity and its rate of change (src/layers/satellites/motion.js).
Every frame each shown point is reckoned from its sample to the world time
and turned into the Earth-fixed frame by the sidereal angle, so points
glide at any play speed. Core satellites still take a fresh sample every
second, and at once when the world time is 30 s from it (fast play, a
seek), which keeps every point within about 10 m of SGP4. Starlink extras
take their first sample as they load and are resampled round-robin, more
per frame the faster time plays (up to 2,000 a frame); a point more than
two minutes from its sample waits for the next one. Hidden points are
moved when shown again, and the tracked satellite keeps its per-frame path.

Measured at globe scale: at 1 min/s points move on every frame, 0.4 px a
frame and at most 1.4 px (before: once a second, 45 px). With 11,880
satellites (Starlink on) the scene holds 60 fps, frames 16.7 ms median and
19.7 ms p95; reckoning costs 0.02 ms a frame for 1,342 points.

scripts/package-boundaries.json

@@ -1854,6 +1854,7 @@
       "src/layers/satellites/interaction.js",
       "src/layers/satellites/labels.js",
       "src/layers/satellites/lifecycle.js",
+      "src/layers/satellites/motion.js",
       "src/layers/satellites/orbits.js",
       "src/layers/satellites/records.js",
       "src/layers/satellites/policy.js",
@@ -2972,6 +2973,7 @@
       "src/layers/satellites/interaction.js",
       "src/layers/satellites/labels.js",
       "src/layers/satellites/lifecycle.js",
+      "src/layers/satellites/motion.js",
       "src/layers/satellites/orbits.js",
       "src/sources/tle.js",
       "src/layers/satellites/records.js",
@@ -4159,6 +4161,7 @@
       "src/layers/satellites/interaction.js",
       "src/layers/satellites/labels.js",
       "src/layers/satellites/lifecycle.js",
+      "src/layers/satellites/motion.js",
       "src/layers/satellites/orbits.js",
       "src/sources/tle.js",
       "src/layers/satellites/records.js",