Fix four defects a user hits in the first minute

Found by surveying the codebase against the plan; each was verified against the
committed assets or the running app before being touched.

TRAPPIST-1 was orbiting the Sun. The Exoplanet Archive leaves sy_dist blank for
some systems, and fetchExoplanets.ts read it with bare Number() — Number('') is
0, which is finite, so it slipped past the Number.isFinite guard in
resolveHostStarId, placed the host at the origin, and matched Sol at distance
exactly 0. 127 records shipped with hostStarId 0, all seven TRAPPIST-1 planets
among them, and the system view filters on that id, so drilling into Sol drew
127 alien worlds inside the real solar system.

Fixed in three places: resolveHostStarId now rejects a non-positive distance
(the robust guard, covering every caller), fetchExoplanets.ts uses the
parseOptionalNumber that already sat unused in that same file for ra/dec/dist,
and validateExoplanets asserts nothing ever resolves to the Sun again — the Sun
has no exoplanets, so that tripwire costs nothing and is permanent.

The archive's endpoint is blocked by this environment's egress policy, so the
ETL cannot be re-run here. The committed asset was corrected in place instead,
which is safe because the outcome is deterministic: the name path runs first and
none of the 127 resolve by name, so all of them reached id 0 positionally and
the fixed pipeline yields null for exactly that set. Cross-referenced hosts drop
from 761 to 634; record count is unchanged.

Dragging to rotate selected stars. Selection was bound to the raw click event,
which browsers fire on release however far the pointer travelled and which
OrbitControls does not suppress — so any drag ending over a star launched a
camera flight, and in system view routed away to /body/:id. Now tracks
pointerdown and ignores a release more than 5 px from it.

Ghost systems accumulated on every star-to-star hop. SystemOrbitsRenderer.dispose
released geometries and materials but never detached its group, so old orbit
lines stayed parented forever — still traversed and re-uploaded each frame with
disposed geometries, drawn over the new system and unpickable. dispose() now
detaches and clears.

Galaxy star labels stayed pinned inside the system view. They are CSS2D objects
parented to the scene rather than to galaxyGroup, so hiding the group left up to
15 parsec-space names clumped over the system's star. Cleared on entry. Also
gated the per-frame Kepler propagation on actually being in a system; it ran in
galaxy view too, because the renderer is never nulled on exit.

Tests: 116 passing, up from 112. Build, both typechecks and the Playwright suite
are green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WaySiNst4HhDXBHnMy8p5G

src/app/shared/astro/host-star-matching.ts

@@ -41,6 +41,14 @@ export function resolveHostStarId(
     return null;
   }
 
+  // A non-positive distance is never a real measurement, and it is the specific shape a
+  // missing CSV cell takes: `Number('')` is `0`, which passes the finiteness check above and
+  // then places the host exactly at the origin — where it matches the Sun at distance 0 and
+  // hands an alien planet to our own solar system.
+  if (query.distancePc <= 0) {
+    return null;
+  }
+
   const hostPosition = raDegDecDistanceToXyz(query.raDeg, query.decDeg, query.distancePc);
   return findNearestStarWithin(hostPosition, stars, toleranceInPc);
 }