fix: correct bitfield decoder using mask extraction, fix command_node

- Switch bitfield decoder from shift-based to mask-based extraction (var>>pos & mask)
  fixes non-power-of-2 bitfields like 6-bit command_node flags
- Fix MultiTypeFix to handle CaseExprTypeOnlyNumber/OnlyBool variants
- Update minecraft-data command_node bitfield order for all 1.21.8+ versions
  to LSB-first convention (matches reverse encoder/decoder)
- Implement SwitchDecoder for extraNodeData via compareTo visitor
- DeclareCommands now decodes successfully (was EOF)
- Add 6 regression tests (entity_equipment, metadata, recipes, commands)

mc/data/minecraft-data/pc/1.21.11/protocol.json

@@ -4120,11 +4120,6 @@
           "type": [
             "bitfield",
             [
-              {
-                "name": "unused",
-                "size": 2,
-                "signed": false
-              },
               {
                 "name": "allows_restricted",
                 "size": 1,
@@ -11697,4 +11692,4 @@
       }
     }
   }
-}
+}