[Feature]: session directory layout adjustment

[zTrix]

Problem

too many directory under sessions directory if running for a long time

Proposal

use codex similar layout

:) 01 $ pwd
/home/user/.codex/sessions/2026/07/01
:) 01 $ ls -l
total 208
-rw-r--r-- 1 user user 209652 Jul  1 12:20 rollout-2026-07-01T12-06-10-019f1bdb-1545-7c42-bcc7-859860a7e832.jsonl

Alternatives considered

No response

Additional context

No response