Function save_to_file 

pub fn save_to_file<Id>(index: &FibSidecarIndex<Id>, path: &Path) -> Result<()>
where
    Id: Clone + Eq + Debug + Serialize,

Serialize a FibSidecarIndex to a binary file.

The file format is FBS1 (see module docs for layout). The profile is serialized as JSON, the Gram table as raw f32 values, and each entry’s FibCodeV1 as compact bytes (to_compact_bytes).

The Id type must implement Serialize (via postcard).

Errors

Returns FibQuantError::CorruptPayload if serialization fails.