HF_DE_PARALLEL_STREAM was restored on every exit path, but the producer
server allows concurrent renders in one process — a router-eligible job's
mutation was still visible to an unrelated render already executing during
that window. Thread the router's decision as a per-render local instead of
a global env var; HF_DE_PARALLEL_STREAM stays as the manual opt-in.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>