strategy: re-export a running subagent for the co-authorship check

liveTaskFilesInCommit read only declared and layout transcript paths, which an in-flight OpenCode record never has, so a running background child gave no evidence that an IDLE parent co-authored a commit. It now resolves the transcript the way condensation does, including the agent's re-export, under a 10 s cap, and the gate is memoized per commit. opencode export runs without git's repo-override variables, since it runs inside git hooks.