PYSEC-2026-3570 Flyto2 Core: ${env.VAR} interpolation reads any env secret despite env.get being denylisted

Summary The capability policy denies the env.get and env.loaddotenv modules by default, with the stated reason that they read arbitrary host environment variables API keys, DSNs and are a secret-exfil risk. But the workflow engine's variable resolver expands $env.VAR for any environment variable...