Function decode_column_value 

pub fn decode_column_value(
    col: &dyn Array,
    data_type: &DataType,
    row: usize,
    crdt_mode: CrdtDecodeMode,
) -> Result<Value, Error>

Decode an Arrow column value to a uni_common::Value, preserving Value::Temporal variants for round-trip fidelity.

For DateTime/Timestamp/Date/Time, delegates to super::arrow_convert::arrow_to_value. For all other types, decodes via value_from_column and converts.