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Add star-map Angular app, ETL pipeline, and caveman plugin

Angular 3D star map (galaxy/system/body views, Three.js rendering,
navigation store) plus the NASA ETL tooling that builds the star,
exoplanet and solar-system datasets, Playwright e2e suite, and the
cs:caveman Claude Code plugin (command, agent, skill).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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src/app/shared/astro/constants.ts

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+/** Astronomical unit conversion and gravitational constants shared by the astro math modules. */
+
+/** Number of astronomical units in one parsec (IAU exact definition). */
+export const AU_PER_PARSEC = 206264.80624709636;
+
+/**
+ * Reference epoch (Julian date, J2000.0) used when orbital data lacks an explicit epoch —
+ * e.g. exoplanets from the NASA Exoplanet Archive only report a handful of elements
+ * (semi-major axis, eccentricity, sometimes argument of periapsis), not a mean-anomaly/epoch
+ * pair. Defaulting the missing epoch to J2000 still lets the body's real orbital period
+ * carry it around a plausible (if not phase-accurate) orbit over time.
+ */
+export const DEFAULT_EPOCH_JD = 2451545.0;
+
+/**
+ * Heliocentric gravitational parameter (GM of the Sun), in AU^3/day^2 — the square of the
+ * Gaussian gravitational constant `k = 0.01720209895 rad/day`. Used to derive a body's mean
+ * motion from its semi-major axis via Kepler's third law.
+ */
+export const GM_SUN_AU3_PER_DAY2 = 0.01720209895 * 0.01720209895;
+
+/**
+ * Approximate planet/Sun mass ratios for the major planets that host moons in `bodies.json`.
+ * Used to derive each planet's gravitational parameter (for propagating its moons) as
+ * `GM_SUN_AU3_PER_DAY2 * massRatio`. Precise enough for visualization; not JPL-grade.
+ */
+const PLANET_TO_SUN_MASS_RATIO: Record<string, number> = {
+  earth: 3.003e-6,
+  mars: 3.227e-7,
+  jupiter: 9.545e-4,
+  saturn: 2.857e-4,
+  uranus: 4.365e-5,
+  neptune: 5.151e-5
+};
+
+/**
+ * Gravitational parameter (AU^3/day^2) to use when propagating a body's orbit: the Sun's
+ * for planets/dwarfs/exoplanets, or the host planet's (derived from its Sun mass ratio) for
+ * moons. Falls back to the Sun's GM if `parentBodyId` isn't a known planet.
+ */
+export function gmForParent(parentBodyId: string | undefined): number {
+  if (!parentBodyId) {
+    return GM_SUN_AU3_PER_DAY2;
+  }
+  const massRatio = PLANET_TO_SUN_MASS_RATIO[parentBodyId];
+  return massRatio ? GM_SUN_AU3_PER_DAY2 * massRatio : GM_SUN_AU3_PER_DAY2;
+}
+
+/** Converts a JS `Date` into a Julian date (days), for driving the Kepler propagator "now". */
+export function dateToJulianDate(date: Date = new Date()): number {
+  return date.getTime() / 86400000 + 2440587.5;
+}