Function resolve_model_root 

pub fn resolve_model_root(config: &RuntimeConfig) -> PathBuf

Resolve the model root: explicit dir, then PDFLUENT_MODEL_DIR, then the per-user default. An empty env var counts as unset, matching ort’s own reading of ORT_DYLIB_PATH.

Public so the install commands put every package file – models and the root-level notices – under the one root the loader reads.