fix(kernel): a small overlap is not taken for bodies apart or inside (#484)

When sample points say two bodies are apart or one is inside the other, the facetings are now checked for surfaces passing through each other; if they do, the boolean is computed instead of shortcut. If it still can't be intersected, the sampled answer is kept as a flagged, unverified result, and Interference lists such pairs as "could not be checked" with the reason. Fixes #442 and #443.

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

crates/kernel/src/boolean_diagnostics.rs

@@ -17,6 +17,9 @@ pub enum BooleanStrategy {
     PlanarFallback,
     ToolNudge,
     Piecewise,
+    /// No retry gave a result, and the answer from sample points was kept although the bodies'
+    /// facetings disagree with it.
+    UnverifiedShortcut,
 }
 
 /// Numerical adjustments used by a successful retry, in millimetres/radians.
@@ -47,6 +50,10 @@ impl BooleanFallback {
             BooleanStrategy::PlanarFallback => "exact planar fallback (no displacement)".into(),
             BooleanStrategy::ToolNudge => format!("tool displacement {:.6e} mm, rotation {:.6e} rad", self.translation_mm, self.rotation_rad),
             BooleanStrategy::Piecewise => "piecewise retry (no displacement)".into(),
+            BooleanStrategy::UnverifiedShortcut => format!(
+                "not verified: the bodies' facets pass through each other by more than {:.6e} mm, but they could not be intersected there; that part is ignored",
+                self.tolerance_mm
+            ),
         }
     }
 }
@@ -66,6 +73,12 @@ impl BooleanDiagnostics {
         }
     }
 
+    /// Why the result is not verified, when it ignores a place where the bodies seem to pass
+    /// through each other ([`BooleanStrategy::UnverifiedShortcut`]).
+    pub fn unverified(&self) -> Option<String> {
+        self.events.iter().find(|event| event.strategy == BooleanStrategy::UnverifiedShortcut).map(BooleanFallback::description)
+    }
+
     pub fn warning(&self) -> Option<String> {
         if self.events.is_empty() && !self.truncated {
             return None;