ResolvedModel
Result of walking a Java item model's parent chain in resolveModel.
Mirrors the flat-builtin / handheld detection rules used by Rainbow's BedrockGeometryContext.java:22-24, 40, which feed into the Bedrock attachable's bedrock_options.display_handheld flag and the 2D-vs-3D branching at conversion time.
Parameters
identifier
the model identifier originally requested
rootParent
the deepest parent in the chain (or null if the model has no parent at all)
mergedJson
merged JSON of the entire parent chain — child keys override parent's
isFlatBuiltin
true if the root parent is one of the vanilla flat-icon parents (minecraft:item/generated or minecraft:builtin/generated)
isHandheldVariant
true if any parent in the chain is a vanilla handheld variant (minecraft:item/handheld, _rod, or _mace)