Function encode_bgra 

pub fn encode_bgra(src: &[u8], w: i32, h: i32, profile: &Profile) -> Vec<u8> 

Encode BGRA pixel data to the format specified by profile.

Returns just the encoded frame data (no 4-byte prefix — caller adds it).

Detection order:

1. clcl_chroma → CLCL encoder
2. cl_chroma → CL encoder
3. profile.encoding → specific encoder

Then applies interlacing and padding if needed.