refactor(schema): rename biome_summary to planet_class (D-188)

"Biome" describes per-zone vegetation classification (Whittaker table).
"Planet class" describes overall planetary character. The conflation
caused the planet generator to misclassify ~270 bodies as barren.

Scope: systems.db column, schema SQL, Rust atlas code, wiki table
headers (Biome → Class), atlas proposal JSONs, all docs/decisions,
tooling scripts. Also normalizes atmosphere vocabulary (breathable →
standard) and expands planet class mapping to all 26 wiki values.
Unknown classes default to temperate for modder safety.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tooling/planet-gen/biomes.toml

@@ -156,13 +156,20 @@ moist_hi = 0.15
 # ─────────────────────────────────────────────────────────────────────
 
 [temperature_bands]
-temperate = [275, 305]
-oceanic   = [278, 300]
-forest    = [275, 308]
-arid      = [295, 340]
-frozen    = [210, 265]
-volcanic  = [290, 380]
-barren    = [180, 380]
+# Core classes
+temperate             = [275, 305]
+oceanic               = [278, 300]
+forest                = [275, 308]
+arid                  = [295, 340]
+frozen                = [210, 265]
+volcanic              = [290, 380]
+barren                = [180, 380]
+# Extended classes
+temperate_terminator  = [260, 310]   # sharp day/night gradient, wide band
+cold_arid             = [240, 290]   # cold desert (Mars-analog)
+hot_arid              = [310, 360]   # scorching desert
+tropical              = [295, 315]   # hot and wet
+boreal                = [245, 278]   # cold forest / taiga
 
 # ─────────────────────────────────────────────────────────────────────
 # Biome color palette

tooling/planet-gen/body_definition_parser.py

@@ -72,12 +72,20 @@ STAR_UV = {
 }
 
 # atmosphere field → density string
+# Wiki atmosphere value → pipeline atmosphere density.
+# Both legacy ("breathable") and current ("standard") wiki values mapped.
 ATMO_MAP = {
-    "none":        "none",
-    "thin":        "thin",
-    "breathable":  "standard",
-    "dense":       "thick",
-    "toxic":       "thick",     # Venus-style reducing atmosphere
+    "none":              "none",
+    "trace":             "none",      # too thin for weather/clouds
+    "thin":              "thin",
+    "breathable":        "standard",  # legacy wiki value
+    "standard":          "standard",  # current wiki value
+    "dense":             "thick",
+    "thick":             "thick",
+    "toxic":             "thick",     # Venus-style reducing atmosphere
+    "reducing":          "thick",     # same as toxic
+    "hydrogen-helium":   "thick",     # gas giant
+    "gas_giant":         "thick",     # gas giant atmosphere field
 }
 
 # hydrosphere → approximate land_fraction range [min, max]
@@ -91,14 +99,44 @@ HYDRO_LAND = {
 }
 
 # biome → planet_class
-BIOME_CLASS = {
-    "temperate":   "temperate",
-    "arid":        "arid",
-    "frozen":      "frozen",
-    "volcanic":    "volcanic",
-    "barren":      "barren",
-    "forest":      "forest",
-    "oceanic":     "oceanic",
+# Wiki planet class → pipeline planet class.
+# All 26 known wiki values mapped explicitly.
+# Unknown values default to "temperate" (safe for modders adding new classes).
+PLANET_CLASS_MAP = {
+    # Direct matches
+    "temperate":              "temperate",
+    "arid":                   "arid",
+    "frozen":                 "frozen",
+    "volcanic":               "volcanic",
+    "barren":                 "barren",
+    "oceanic":                "oceanic",
+    # Temperate variants
+    "temperate_terminator":   "temperate_terminator",
+    "temperate-cool":         "temperate",
+    "temperate_highland":     "temperate",
+    "temperate_maritime":     "temperate",
+    "temperate_savanna":      "temperate",
+    "temperate_coastal":      "temperate",
+    "temperate_riverine":     "temperate",
+    "temperate_ocean":        "oceanic",
+    "cold_temperate":         "temperate",
+    "floodplain_temperate":   "temperate",
+    # Arid variants
+    "cold_arid":              "cold_arid",
+    "hot_arid":               "hot_arid",
+    # Tropical
+    "tropical":               "tropical",
+    "tropical_ocean":         "oceanic",
+    "subtropical":            "tropical",
+    # Cold
+    "ice":                    "frozen",
+    "boreal":                 "boreal",
+    # Warm ocean
+    "warm_ocean":             "oceanic",
+    # Geothermal
+    "geothermal":             "volcanic",
+    # Forest (from prototype)
+    "forest":                 "forest",
 }
 
 # planet_class → axial tilt range [min, max] degrees
@@ -414,7 +452,9 @@ def _build_body_def(
     if btype == "gas_giant" or mass in ("gas_giant", "ice_giant"):
         planet_class = "gas_giant"
     else:
-        planet_class = BIOME_CLASS.get(biome, "barren")
+        planet_class = PLANET_CLASS_MAP.get(biome, "temperate")
+        if biome and biome not in PLANET_CLASS_MAP and biome != "—":
+            log.warning(f"  {bid}: unknown planet class '{biome}' — defaulting to temperate")
 
     planet_class = ov.get("planet_class", planet_class)