strategy: resolve Codex subagent transcripts through the inventory at condensation

A Codex child's rollout path reaches its task record only when the parent's turn-end inventory refresh sees a terminal turn. When the parent commits mid-turn (after the child finished, before its own Stop), condensation saw a record with no path, the Claude-layout fallback could not find a Codex rollout, and the checkpoint stored a reason-only task.json.

materializeTaskRecords now offers records whose declared path is missing or no longer exists to the agent's inventory-aware extractor, which accepts a rollout only when its session_meta.id matches the agent ID. This also covers rollouts Codex archived after their path was recorded.