fix: batch-3 adversarial review findings

feat: K8s corpus config entry, ingestion target, curation policy

security: fail-closed on secret extraction and env var leakage

refactor: address batch-1 review feedback

feat: multi-corpus construction with nested corpus×provider composition

feat: runtime provider switching via dashboard toggle

fix(security): add security to /ask/stream, wire PII redactor into SearchTool

feat(security): wire injection detection, output validation, audit into pipeline

feat: add SQLite conversation sessions with session_id

feat: switch deployment to Hugging Face Spaces (16GB free tier)

fix: skip startup warmup in production to avoid OOM on 512MB

feat: Render deployment config, startup warmup, README update

feat: add provider retry with backoff and API rate limiting

feat: add cross-encoder reranking with feature flag

feat: add grounded refusal gate based on retrieval score threshold

feat: Day 6 — serving layer with FastAPI app, routes, middleware