feat: add e2e pipeline verification example (49 checks, all pass)

Comprehensive end-to-end test covering:
- Data file verification (SNOMED thesaurus, UMLS artifact, CPIC, UMLS TSV)
- KG population with 18 nodes, 14 edges, IS-A hierarchy traversal
- Treatment lookups and contraindication checks via adjacency index
- Symbolic embeddings with similarity scoring
- Entity extraction via Aho-Corasick (7 entities in 0.012ms)
- UMLS artifact loading (1.4M patterns, 4.3M concepts from 199MB)
- PGx validation (CYP2C19, CYP2D6 metabolizer profiles)
- MedGemma inference (mock client, Osimertinib recommendation)
- Full 6-step consultation pipeline

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: AlexMikhalev