Implement Pipeline::load/suggest for Mode C: lexical search per segment,
cross-segment dedup via fusion, tag derivation, filter application.
Add meta_lookup fallback (exact → strip trailing 0 → 3-char root) to
bridge the ICD code granularity gap between the corpus (E11.90-style
6-char codes) and ClaML (which only stores E11, E11.0-style entries).
