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- Delete tooling/atlas-helpers.sh (superseded by clean scripts on main)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/GJ845.json

@@ -1,7 +1,7 @@
 {
   "system_id": "GJ 845",
   "proper_name": "Cairn",
-  "star_type": "M",
+  "star_type": "K",
   "spectral_class": "K5V",
   "wiki_data": {
     "habitable_count": 2,
@@ -70,7 +70,7 @@
       "economic_role": null,
       "settlement_pattern": null,
       "industrial_corridor": null,
-      "notes": "habitable, garden-grade — nobody lives here"
+      "notes": "habitable, garden-grade \u2014 nobody lives here"
     },
     {
       "body_id": "GJ845d-1",
@@ -110,7 +110,7 @@
       "economic_role": null,
       "settlement_pattern": null,
       "industrial_corridor": null,
-      "notes": "second habitable — also empty"
+      "notes": "second habitable \u2014 also empty"
     },
     {
       "body_id": "GJ845f",
@@ -201,7 +201,7 @@
       "inhabited": false,
       "population": 0,
       "mass_class": "dwarf",
-      "surface_gravity": 0.10,
+      "surface_gravity": 0.1,
       "orbital_period_days": 4.0,
       "rotation_period_hours": 96,
       "atmosphere": "none",