Pass the requesting operation into the descriptor failure owner. Discovery retains its own identity; command execution and completion confirmation retain cutter_command with exact cleanup dependencies.
Validated 61 focused tests across five files, including denied retry and successful native descriptor release. Controlled close faults; no native Cutter engine verified.
Refs: #4634
Refs #4471, #3946.
Read only admitted regular descriptors without blocking on pipes. Retain failed closes, join discovery workers, and propagate cancellation through CLI and MCP. Preserve command and descriptor cleanup as independent owners.