Slow orbital periods for readability at galaxy-inspection scale

- Introduce ORBITAL_PERIOD_SCALE = 4.0 multiplier so planets/stations/
  gas clouds/anomalies all orbit visibly slower. At inspection-scale
  zoom the un-scaled periods (≈2.5s per unit of radius) made bodies
  spin like tops; tuned for a calm browsing pace.
- Default Orbit angular_velocity 0.5 → 0.15 (≈40s per revolution).
- Update orbital_period unit tests for the new scale factor.

apps/game/src/gameplay/galaxy/contents.rs

@@ -295,9 +295,15 @@ const ASTEROID_COLOR_COUNT: usize = 5;
 /// asteroid rocks. Stargates are intentionally excluded — they stay
 /// stationary as navigational aids. Periods are floored at
 /// [`MIN_ORBITAL_PERIOD`] so very tight orbits don't become a blur.
+///
+/// [`ORBITAL_PERIOD_SCALE`] then multiplies the raw period so all bodies
+/// orbit visibly slower — at galaxy-inspection scale the un-scaled periods
+/// (≈2.5 s per unit of radius) made planets spin like tops. Tuned for
+/// readable motion when the player is browsing the galaxy map.
 const MIN_ORBITAL_PERIOD: f32 = 2.0;
+const ORBITAL_PERIOD_SCALE: f32 = 4.0;
 fn orbital_period(orbit: f32, jitter: f32) -> f32 {
-    (orbit * 2.5 + jitter).max(MIN_ORBITAL_PERIOD)
+    ((orbit * 2.5 + jitter) * ORBITAL_PERIOD_SCALE).max(MIN_ORBITAL_PERIOD)
 }
 
 // ─── Generation ─────────────────────────────────────────────────────────────
@@ -1239,10 +1245,11 @@ mod tests {
 
     #[test]
     fn orbital_period_grows_linearly_with_radius() {
-        // No jitter → period = 2.5 × orbit.
+        // No jitter → period = 2.5 × orbit × scale.
+        let scale = ORBITAL_PERIOD_SCALE;
         assert!((orbital_period(0.0, 0.0) - MIN_ORBITAL_PERIOD).abs() < 1e-6);
-        assert!((orbital_period(2.0, 0.0) - 5.0).abs() < 1e-6);
-        assert!((orbital_period(8.0, 0.0) - 20.0).abs() < 1e-6);
+        assert!((orbital_period(2.0, 0.0) - 5.0 * scale).abs() < 1e-5);
+        assert!((orbital_period(8.0, 0.0) - 20.0 * scale).abs() < 1e-5);
     }
 
     #[test]
@@ -1254,9 +1261,10 @@ mod tests {
 
     #[test]
     fn orbital_period_applies_jitter_additively() {
+        // Jitter is added before the scale, so the delta is jitter × scale.
         let base = orbital_period(5.0, 0.0);
         let jittered = orbital_period(5.0, 2.0);
-        assert!((jittered - base - 2.0).abs() < 1e-6);
+        assert!((jittered - base - 2.0 * ORBITAL_PERIOD_SCALE).abs() < 1e-5);
     }
 
     #[test]

apps/game/src/gameplay/movement/orbit.rs

@@ -24,7 +24,9 @@ impl Default for Orbit {
     fn default() -> Self {
         Self {
             angle: 0.0,
-            angular_velocity: 0.5,
+            // ~1 full revolution every 40 seconds — calm enough to read at
+            // inspection-scale zoom levels. Callers can override per-instance.
+            angular_velocity: 0.15,
             radius: 10.0,
             plane: OrbitPlane::Horizontal,
         }