Transform Codex spawn_agent/wait_agent/close_agent into unified Agent
card display: rewrite spawn_agent as "Agent" tool with subagent_type,
prompt, and description; correlate final results from wait_agent and
close_agent outputs; parse sub-agent session JSONL files for nested
tool call lists; suppress intermediate status messages during agent
execution; clean exec_command output to show only the command and its
result.
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