在 Claude 代码记录中, session-end transcript back-fill 无法提取提示信息

`extractTranscriptPrompts` in `src/hooks/session-end.ts` returns an empty array for every Claude Code transcript, so the prompt back-fill added for the SessionEnd hook silently posts nothing. Sessions then reach the daemon carrying only `{endedAt, status}`, and `mem::summarize` logs `No observations to summarize` for them indefinitely.