Local log active-session guard

Motivation

Long-running local services such as the Celery worker can keep writing logs while other local-run tasks start later. The local log cleanup kept only the newest session directories and could delete a still-active worker session, causing the log mirror to fail with cannot redirect to worker.log.1 and terminating the wrapper with exit code 143.

User-facing change

scripts/dev/run-with-log.sh now writes per-service active markers into the selected log session and skips cleanup for sessions whose marker PID is still alive. Stale markers are removed automatically during cleanup.

API/IaC diff summary

• Local development script only; no API or infrastructure changes.

Validation evidence

• bash -n scripts/dev/run-with-log.sh scripts/dev/local-run.sh
• Restarted scripts/dev/local-run.sh worker and verified .active.worker.<pid> exists in the live log session.