Local Codex logs should respect system timezone

Some Codex local logs still use UTC instead of the machine's local timezone.

I'm on macOS with GMT+8. Right now the behavior seems mixed:

• rollout filenames use local time
• but timestamps inside rollout JSONL records still use UTC (Z)
• session logs also use UTC

From the code:

• codex-rs/core/src/rollout/recorder.rs uses now_local() for rollout filenames
• the same file still uses now_utc() for JSONL record timestamps
• codex-rs/tui_app_server/src/session_log.rs also uses chrono::Utc::now()

This makes local debugging annoying because Codex logs don't line up cleanly with terminal output, editor activity, and other local logs.

Request:
please make local log output use the system timezone consistently, or add a config/env option to choose local time instead of UTC.