Builds a structural signature from a top-level ECharts option object.
The signature captures only the shape - not the values - of the option.
Shape changes (removed keys, removed array items) are what drive merge
strategy decisions; value changes are handled by ECharts' normal merge.
Builds a structural signature from a top-level ECharts option object. The signature captures only the shape - not the values - of the option. Shape changes (removed keys, removed array items) are what drive merge strategy decisions; value changes are handled by ECharts' normal merge.