kernel-ladder: 10/008 grades the vents as four times one

It passed on one valid body alone. Each d3 vent goes through the shelled
top skin into the cavity and meets nothing else, so the case is 09/011
less 4 pi 1.5^2 1.5; with the bbox. Holds on SMLib (1e-6 relative).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/kernel-cases/ladder/10-patterns-and-mirrors/008-part-vents/expected.json

@@ -1,7 +1,23 @@
 {
  "sources": [],
  "what": "the running part with a d3 vent hole in its top patterned 4 times at 5 mm",
- "source": "invariants",
- "method": "holes through the shelled top skin; one valid body",
- "body_count": 1
+ "source": "analytic",
+ "method": "pattern = 4 x the feature: each d3 vent goes through the shelled top skin (z 18.5..20) into the cavity and meets nothing else (the M6 hole's tube is 7.3 away, the wall's 6 past y = 24): V = 09/011 - 4 pi 1.5^2 1.5; the bbox is the part's",
+ "body_count": 1,
+ "volume_mm3": 15355.301474157,
+ "bbox": {
+  "min": [
+   0,
+   0,
+   0
+  ],
+  "max": [
+   60,
+   40,
+   35
+  ]
+ },
+ "tolerance": {
+  "rel": 0.0001
+ }
 }

tools/kernel-ladder/cases.py

@@ -1071,7 +1071,9 @@ case(T10, "007-pattern-bodies", "a pin r3 h10 patterned 4 times at 10 mm as bodi
      {"body_count": 4, "volume_mm3": 4 * PI * 9 * 10, "faces": 12}, "four separate pins")
 case(T10, "008-part-vents", "the running part with a d3 vent hole in its top patterned 4 times at 5 mm",
      [H(position=[30, 24, 20], diameter=3, name="Vent"), C("solid.pattern.rectangular", features=["Vent"], dir1=[1, 0, 0], count1=4, spacing1=5)],
-     {"body_count": 1}, "holes through the shelled top skin; one valid body", base=C9, source="invariants")
+     {"body_count": 1, "volume_mm3": V9 - 4 * PI * 1.5 ** 2 * 1.5, "bbox": {"min": [0, 0, 0], "max": [60, 40, 35]}, "tolerance": {"rel": 1e-4}},
+     "pattern = 4 x the feature: each d3 vent goes through the shelled top skin (z 18.5..20) into the cavity and meets nothing else (the M6 hole's tube is 7.3 away, "
+     "the wall's 6 past y = 24): V = 09/011 - 4 pi 1.5^2 1.5; the bbox is the part's", base=C9)
 C10 = up(T10, "008-part-vents")
 
 # ---------------------------------------------------------------- 11 cumulative parts