fix(kp): place exact angular boundaries on the opening subdivision

Upstream 8eec9a54. Floating accumulation and a 120-degree remainder put star, pada, and sub-lord on different sides of the same boundary. Random longitudes away from those boundaries are unchanged. BUG-1383.

Co-Authored-By: Grok (agent loop)
Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_kp_exact_angular_boundaries.py

@@ -0,0 +1,42 @@
+"""Synthetic angular fixtures; no birth records or predictive assertions."""
+from fractions import Fraction
+import math
+import pytest
+from scripts.kp_system import get_kp_lords
+
+ORDER='Ketu Venus Sun Moon Mars Rahu Jupiter Saturn Mercury'.split()
+YEARS=(7,20,6,10,7,18,16,19,17)
+
+
+def test_every_subsub_boundary_is_left_closed_right_open():
+    starts=[]
+    for star in range(27):
+        start=Fraction(star*40,3)
+        for offset in range(9):
+            sub=(star+offset)%9;span=Fraction(40*YEARS[sub],360)
+            for child_offset in range(9):
+                child=(sub+child_offset)%9
+                starts.append((float(start),ORDER[sub],ORDER[child]))
+                start+=span*YEARS[child]/120
+    for i,(angle,sub,child) in enumerate(starts):
+        for probe in (angle,math.nextafter(angle,math.inf)):
+            actual=get_kp_lords(probe)
+            assert (actual['sub_lord'],actual['sub_sub_lord'])==(sub,child)
+        if i:
+            before=get_kp_lords(math.nextafter(angle,-math.inf))
+            assert (before['sub_lord'],before['sub_sub_lord'])==starts[i-1][1:]
+
+
+def test_quarter_boundaries_and_wrap():
+    for i in range(108):
+        degree=float(Fraction(10*i,3))
+        assert get_kp_lords(degree)['pada']==i%4+1
+        if i:assert get_kp_lords(math.nextafter(degree,-math.inf))['pada']==(i-1)%4+1
+    assert get_kp_lords(70)['pada']==2
+    assert get_kp_lords(360)==get_kp_lords(0)
+    assert get_kp_lords(-1)==get_kp_lords(359)
+
+
+@pytest.mark.parametrize('invalid',[True,None,'70',float('nan'),float('inf'),float('-inf')])
+def test_nonfinite_or_nonnumeric_longitude_rejected(invalid):
+    with pytest.raises(ValueError):get_kp_lords(invalid)