Rename the middle rain tiers and merge Mod–Heavy into Heavy (#214)

The rain-intensity scale drops its two hyphenated compound labels for single
words and loses a tier, going from eight to seven:

  Trace / Light / Brisk / Typical / Heavy / Very Heavy / Extreme

- Light–Mod -> Brisk, Moderate -> Typical (renames only; classes unchanged).
- Mod–Heavy is merged up into Heavy, whose floor drops from the 75th to the 60th
  rain-day percentile, so Heavy now spans 60–90.
- The lightest tier (already the merged Very Light) is renamed Trace.

grading.py RAIN_BANDS and the frontend SCALE_RAIN mirror stay in lockstep, and
the detail-view ladder derives from the table so it follows automatically. The
now-unreferenced wet-6 colour token is kept so any day still cached under that
class renders until the derived store recomputes; the chart's percentile fan also
keeps it for a smooth gradient.

Claude-Session: https://claude.ai/code/session_013dRZmX9D3JEntfMKWMTWZ8

grading.py

@@ -47,19 +47,17 @@ TEMP_BANDS = [
 
 # Precipitation is graded ONLY among days that actually rained (>= RAIN_THRESHOLD)
 # in the seasonal window — a "rain percentile". Rain is one-directional (heavier =
-# more extreme), so these 8 tiers are sequential light->heavy, using the SAME cut
+# more extreme), so these 7 tiers are sequential light->heavy, using the SAME cut
 # points as temperature. Dry days are handled separately (the "dry" class, colored
 # by dry streak in the UI). Same [lower, upper) convention as TEMP_BANDS.
 RAIN_BANDS = [
     (99, "Extreme", "wet-9"),       # heaviest rain for the season (darkest)
     (90, "Very Heavy", "wet-8"),    # 90-99
-    (75, "Heavy", "wet-7"),         # 75-90
+    (60, "Heavy", "wet-7"),         # 60-90  (the old Mod–Heavy tier merged in)
-    (60, "Mod–Heavy", "wet-6"),     # 60-75
+    (40, "Typical", "wet-5"),       # 40-60  (was Moderate)
-    (40, "Moderate", "wet-5"),      # 40-60
+    (25, "Brisk", "wet-4"),         # 25-40  (was Light–Mod)
-    (25, "Light–Mod", "wet-4"),     # 25-40
     (10, "Light", "wet-3"),         # 10-25
-    (0, "Very Light", "wet-2"),     # <10   the lightest measurable rain (was two
+    (0, "Trace", "wet-2"),          # <10    the lightest measurable rain
-                                    #       tiers, Very Light + Trace, now merged)
 ]
 
 

tests/test_grading.py

@@ -69,11 +69,11 @@ def test_dry_day_gets_dry_class_without_percentile():
 
 def test_rain_percentile_ranks_among_rain_days_only():
     # 7 dry days + rain days [0.1, 0.2, 0.4]; 0.2 ranks among the 3 rain days:
-    # less=1, equal=1 -> (1 + 0.5) / 3 = 50% -> Moderate, unaffected by the dry mass.
+    # less=1, equal=1 -> (1 + 0.5) / 3 = 50% -> Typical, unaffected by the dry mass.
     samples = np.array([0.0] * 7 + [0.1, 0.2, 0.4])
     g = grading._grade_precip(samples, 0.2)
     assert g["percentile"] == 50.0
-    assert g["grade"] == "Moderate"
+    assert g["grade"] == "Typical"
 
 
 def test_rain_with_no_historical_rain_days_is_extreme():
@@ -81,16 +81,22 @@ def test_rain_with_no_historical_rain_days_is_extreme():
     assert g["percentile"] == 100.0 and g["class"] == "wet-9"
 
 
-def test_lightest_rain_day_grades_very_light_not_trace():
+def test_rain_scale_labels_and_merges():
-    # The former "Trace" tier (<1st percentile of rain days) was merged into
+    # The seven-tier scale: Trace / Light / Brisk / Typical / Heavy / Very Heavy /
-    # "Very Light", which now bottoms out the scale at 0.
+    # Extreme. Light–Mod and Moderate were renamed; Mod–Heavy was merged up into
-    assert "Trace" not in [b[1] for b in grading.RAIN_BANDS]
+    # Heavy (which now floors at the 60th percentile).
-    assert grading.RAIN_BANDS[-1] == (0, "Very Light", "wet-2")
+    labels = [b[1] for b in grading.RAIN_BANDS]
-    rain = np.arange(1, 201, dtype=float) / 100.0     # 200 rain days: 0.01 .. 2.00
+    assert labels == ["Extreme", "Very Heavy", "Heavy", "Typical", "Brisk", "Light", "Trace"]
+    for gone in ("Very Light", "Light–Mod", "Moderate", "Mod–Heavy"):
+        assert gone not in labels
+    # A rain day at the old Mod–Heavy range (60–75 pct) is now Heavy.
+    rain = np.arange(1, 201, dtype=float) / 100.0
     samples = np.concatenate([np.zeros(20), rain])
-    g = grading._grade_precip(samples, 0.01)           # the very lightest -> <1 pct
+    g = grading._grade_precip(samples, 1.35)           # ~67th percentile of rain days
-    assert g["percentile"] < 1
+    assert 60 <= g["percentile"] < 75 and g["grade"] == "Heavy" and g["class"] == "wet-7"
-    assert g["grade"] == "Very Light" and g["class"] == "wet-2"
+    # The lightest measurable rain is Trace, bottoming the scale at 0.
+    g0 = grading._grade_precip(samples, 0.01)
+    assert g0["grade"] == "Trace" and g0["class"] == "wet-2"
 
 
 # ---- dry streaks ---------------------------------------------------------------