`Encoder` class lacks a `code` property exposing the prefix byte

[sumanjeet0012]

The Encoder class stores the prefix code internally as self._codec.code but doesn't expose it as a public property. Users who need the prefix byte must access the private _codec attribute or call get_encoding_info().

Problem

enc = Encoder("base16")
enc.encoding   # "base16" ✅ — name is public
enc.code       # ❌ AttributeError — prefix byte not exposed
enc._codec.code  # b"f" — works but accesses private attribute

Go's Encoder exposes the encoding code:

func (p Encoder) Encoding() Encoding {
    return p.enc  // Returns the Encoding constant (e.g., Base16 = 'f')
}

Proposed Solution

Add a code property to the Encoder class:

class Encoder:
    @property
    def code(self) -> bytes:
        """The multibase prefix byte for this encoding."""
        return self._codec.code

Add tests and update __init__.py exports if needed.

Related

• Go equivalent: Encoder.Encoding() method in go-multibase encoder.go