An opaque, process-owned Decibel session handle.

Session handles may only be used by the process that created them and cannot be transferred. Calls from another process raise Decibel.SessionError with reason: :not_owner, even after the owner closes the session or exits. Session state lives until Decibel.close/1 is called or the owner process exits, and the owner's operations on a closed handle use reason: :closed.

Their fields are private implementation details and must not be inspected, altered, or constructed by callers. See Decibel's Ownership and lifetime section for the complete concurrency, supervision, phase, and lifecycle contract.