Raycasts: take a state's context rule from its collision flag

The name test (scaffolding, powder_snow) missed the liquid rule, so with
an entity's context a lava block took its cached empty shape, where
collision_shape_with_context gives a strider the lava's stable shape.
Read the registry's contextual flag instead, as collision_shape_with_context
does.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/horizon-client/src/mobs/world.rs

@@ -297,10 +297,9 @@ impl MobWorld<'_> {
             if !self.collision.may_collide(state) {
                 return None;
             }
-            let is_contextual = context.is_some() && {
-                let name = &self.facts.get(state).name;
-                name.ends_with("scaffolding") || name.ends_with("powder_snow")
-            };
+            // Scaffolding, liquids (a strider stands on lava) and powder snow
+            // take the entity's context; every other state has its cached shape.
+            let is_contextual = context.is_some() && self.collision.has_context_rule(state);
             if !is_contextual
                 && let Ok(Some(shape)) = self.collision.cached_shapes().cached_shape(state)
             {

crates/horizon-world/src/block_collision.rs

@@ -174,6 +174,14 @@ impl<'r> BlockCollisionRegistry<'r> {
             .get(state.0 as usize)
             .is_none_or(|flags| flags & 4 == 0)
     }
+    /// Whether `state` has a contextual collision rule (scaffolding, a liquid, powder snow):
+    /// its shape with an entity's context may differ from the cached one. States outside the
+    /// registry count.
+    pub fn has_context_rule(&self, state: BlockStateId) -> bool {
+        self.scan_flags
+            .get(state.0 as usize)
+            .is_none_or(|flags| flags & 8 != 0)
+    }
     /// Whether a scan keeps `state` in the cells around its box: a large
     /// collision shape or a moving piston. States outside the registry count.
     pub fn reaches_out(&self, state: BlockStateId) -> bool {