fix(atlas): address PR #100 review — star_type audit, data quality fixes

- Fix star_type/spectral_class mismatches across 36 proposals
- Differentiate GJ1002 copy-paste planets (c-g had identical params)
- Fix GJ880 malformed spectral_class (M2: → M2V) and Leirvik station pop
- Fix GJ3325 malformed spectral_class (K: → K)
- Correct white dwarf star_type (GJ1221, GJ3991 → D)
- Correct "unusual" star_type (GJ3877, GJ661A → K)
- Delete tooling/atlas-helpers.sh (superseded by clean scripts on main)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/atlas/proposals/GJ699.json

@@ -1,7 +1,7 @@
 {
   "system_id": "GJ 699",
   "proper_name": "Barnard's Star",
-  "star_type": "K",
+  "star_type": "M",
   "spectral_class": "sdM4",
   "wiki_data": {
     "habitable_count": 1,
@@ -81,7 +81,7 @@
       "inhabited": false,
       "population": 0,
       "mass_class": "terrestrial",
-      "surface_gravity": 0.40,
+      "surface_gravity": 0.4,
       "orbital_period_days": 400,
       "rotation_period_hours": 15.0,
       "atmosphere": "thin",