Tasks

• Reproduce retained input after close; verify death and actual shutdown exit.
• Select a bounded I/O design with original-PTY identity and partial evidence.
• Make lifecycle cancellation and reader behavior explicit.
• Verify timeout/close/death/shutdown.
• Complete existing IPC regressions on the rebased integration.
• Complete full checks.
• Complete independent review.
• Publish, link and merge on exact-head CI.