fix: Add missing CBOR type support in Option deserialization
The PrefetchedDeserializer (used for Option<T>) was missing support
for three major CBOR types, causing deserialization failures:
- MAJOR_TAG (type 6): Failed with "Unsupported type in option" error
- Now supports: Option<DateT>, Option<Tagged<T>>
- MAJOR_ARRAY (type 4): Would have failed for Option<Vec<T>>
- Now supports: Option<Vec<T>>, Option<[T; N]>
- MAJOR_MAP (type 5): Would have failed for Option<HashMap<K,V>>
- Now supports: Option<HashMap<K,V>>, Option<StructType>
Added comprehensive tests for all three cases. All 204 tests passing.
Fixes issue with DateT deserialization in Option fields.