Keep provider task identifiers opaque and use left joins for cleanup so
deleting the environment or run does not strand an existing lease. Require
live records for admission and connection, and retain the pinned plugin
for cleanup with nullable context. Test connection credentials, expired
leases, removed context, and opaque identifiers.
Verified 18 focused tests, SDK build, and server typecheck.
Co-Authored-By: Paperclip <noreply@paperclip.ing>
