Draw each HYG star at Gaia's distance, and keep the ones Hipparcos misplaced

HYG and Gaia were both cut at 250 pc, each on its own distance. A star
Hipparcos put at 200 pc and Gaia at 300 was kept by the first, never
downloaded from the second, and drawn at 200. That is where 83% of the
9 691 mid-magnitude HYG stars without a Gaia counterpart came from, and at
the median Hipparcos had them a third too close. The mirror case, Hipparcos
outside and Gaia inside, dropped the HYG row and left its Gaia entry
anonymous.

Gaia's own Hipparcos cross-match (hipparcos2_best_neighbour, a fixed DR3
table of 99 525 rows) gives a usable Gaia distance for 97 751 of them.
placementDistancePc keeps a star either survey puts inside the cutoff, and
draws every kept star at the better measurement, inside the cutoff or not.
57 121 HYG stars now sit at Gaia's distance. 6 833 of them are past 250 pc:
Zet Per 230 -> 259 pc, 35 Ori 137 -> 330, 44 Cnc 223 -> 613, and the
farthest, HIP 69445, at 8.7 kpc. 3 666 stars that Hipparcos put outside are
now kept, and 3 656 of them give a Gaia entry its name.

The cross-match is required rather than skipped when unreachable. Without
it, every one of those stars would move back to its Hipparcos distance, and
the published map would flip with the archive's availability. The ESA TAP
answered it with a 500 at first and in 102 s on the next try. So fetches
now retry 5xx and network failures twice, after 30 s and 120 s, in the
fetch every source goes through. The refresh job also carries the Gaia DR3
responses from run to run in the Actions cache: the release is frozen, and
a live re-fetch has already reproduced stars.bin byte for byte.

423 651 stars (+10), 61 168 HYG rows folded into Gaia entries (+3 656),
351 597 unnamed designations (-3 656). 10 886 HYG survivors and 23 unmerged
pairs under an arcsecond, both inside the merge gate's ceilings. The same
1 972 exoplanets have a host; KELT-4 A b and MWC 758 c now sit on their
named star.

The HUD's "Radius" becomes "Survey radius": 250 pc is where Gaia is
surveyed to, and no longer the edge of the map.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jxMkwA2rbicdGxHosecYi

tools/etl/sources/registry.ts

@@ -14,7 +14,8 @@ export const STAR_SOURCES: readonly StarSource[] = [
     name: 'HYG database (Hipparcos, Yale Bright Star, Gliese)',
     role: 'positional',
     endpoint: 'https://raw.githubusercontent.com/astronexus/HYG-Database',
-    contributes: 'A complete, named, spectrally classified bright-star catalogue with parallaxes — 68388 stars within 250 pc.',
+    contributes:
+      'A complete, named, spectrally classified bright-star catalogue. Its Hipparcos parallaxes give way to Gaia’s wherever Gaia has a usable one, so its stars sit where the better measurement puts them.',
     unimplementedBecause: null
   },
   {