fix(scaffold,invmanager): stop treating cobwebs as placeable blocks

Cobwebs are BlockItems, so BlockUtil.isPlaceable treated them like
ordinary building blocks: Scaffold would select them and bridge with
them, and InventoryManager counted them toward Max Block Size, then
threw the web stack away via getWorstBlock once over the limit.
Exclude WebBlock so webs stay reserved for AutoWebPlace/manual use.

Fixes #50

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/main/java/shit/zen/utils/game/BlockUtil.java

@@ -20,6 +20,7 @@ import net.minecraft.world.level.block.LadderBlock;
 import net.minecraft.world.level.block.LiquidBlock;
 import net.minecraft.world.level.block.SlabBlock;
 import net.minecraft.world.level.block.TntBlock;
+import net.minecraft.world.level.block.WebBlock;
 import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.phys.AABB;
 import net.minecraft.world.phys.shapes.Shapes;
@@ -122,6 +123,10 @@ extends ClientBase {
             if (block instanceof SlabBlock) {
                 return false;
             }
+            // Cobwebs are tactical utility items (AutoWebPlace ammo), never bridging blocks.
+            if (block instanceof WebBlock) {
+                return false;
+            }
             return !blacklist.contains(block);
         }
         return false;