feat: retrieval grounding, trial quality, and drug-name typo suggestions

feat: automate ALS seed entities from trials and paper corpus

feat(trials): replace hardcoded entity regex with LLM extraction

feat: Stage 4 — entity extraction + knowledge graph + KG-expanded RAG

feat: Stage 3 — RAG pipeline + working end-to-end query

fix(pmc): add rich progress bar to get_pmcids (499 calls, ~3 min)

feat: initial project scaffold and Stage 2 ingestion pipeline