Function from_msgpack 

pub fn from_msgpack(
    _msgpack: &[u8],
    _doc: &LemmaDoc,
    _all_docs: &HashMap<String, LemmaDoc>,
) -> Result<Vec<String>, LemmaError>

Convert MsgPack fact overrides to Lemma syntax strings

MsgPack provides typed values, which we convert to Lemma syntax:

• Strings: quoted text
• Numbers: numeric literals
• Booleans: true/false
• Binary data: base64 encoded strings for appropriate types

This is a stub implementation. Full MsgPack support requires:

• Add rmp-serde dependency
• Deserialize MsgPack to intermediate format
• Map to Lemma types using schema
• Serialize to Lemma syntax strings