Give a luminosity below a hundredth of the Sun's two figures, so Proxima reads 0.0015 L☉ not 0.002

formatLuminosity printed three decimals from a thousandth to 1 L☉, which leaves one figure below
a hundredth. d94451e put the archive's own luminosity on the card, and Proxima's 1.51×10⁻³ L☉
(st_lum −2.821 ± 0.02 dex) read 0.002, 32 % over and six times the archive's error bar, while
8.9×10⁻⁴ just below the cut kept its two figures. Below 0.01 it is now two significant figures.

Over the 4 440 hosts exoplanets.json gives a luminosity for: 23 printed more than 10 % off it and
43 more than 5 % before (worst 32.5 %); none more than 5 % after (worst 4.4 %). In the app on
:4302, Proxima's card reads "Luminosity 0.0015 L☉".

Tests: quantity.spec now expects 0.0017 → "0.0017 L☉" and Proxima's figure → "0.0015 L☉", and
keeps 0.0523 and 0.523 at three decimals; star-readouts.spec and the scene spec now expect
"0.0015 L☉" where they pinned "0.002". Controls: three decimals below a hundredth, and two figures
reaching up to 1, each fail the named test.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/app/features/galaxy-system/galaxy-system-scene.component.spec.ts

@@ -1010,7 +1010,7 @@ describe('GalaxySystemSceneComponent camera-flight transitions', () => {
       expectColour(scene.starTint.value, blackbodyColor(2900));
       const light = scene.systemRenderer.object.children.find((child): child is THREE.PointLight => child instanceof THREE.PointLight)!;
       expectColour(light.color, blackbodyColor(2900, SOLAR_EFFECTIVE_TEMPERATURE_K));
-      expect(scene.hudReadouts().find((readout) => readout.label === 'Luminosity')).toEqual({ label: 'Luminosity', value: '0.002 L☉' });
+      expect(scene.hudReadouts().find((readout) => readout.label === 'Luminosity')).toEqual({ label: 'Luminosity', value: '0.0015 L☉' });
       expect(scene.hudReadouts().find((readout) => readout.label === 'Radius')?.value).toBe('0.141 solar radii');
     });