Adds three integration tests gated by FEDERATED_INTEGRATION=1 that exercise
the federated tier against a live docker-compose federated profile:
- federated-boot.success — detectAndAssertTier resolves; pg_extension lists vector
- federated-boot.pg-unreachable — fail-fast TierDetectionError(service=postgres)
using OS-reserved closed port to avoid host-port collisions
- federated-pgvector — TEMP table with vector(3) column round-trips data
Real services, no mocks. Tests skip cleanly when env var is unset.
Refs #460
