feat(runtime): allow event log output directory to be configured in workflow.yaml

Summary

Event logs are always written to $TMPDIR/conductor/ (typically /tmp/conductor/) with no way to configure the output directory.

Problem

・Event logs in tmp are lost on reboot or tmpwatch cleanup
・Users must manually copy event logs to a persistent directory after each run
・When a workflow crashes without a workflow_failed event, the only diagnostic is the event log -- which may already be gone
・The event log subscriber is always-on by design (correct -- it's a flight recorder), but the output location should be user-configurable
・Configurable log output directories are standard in self-hosted orchestration tools: Airflow(base_log_folder), Argo workflows(artifactRepository), Temporal, Prefect, Docker(log-driver), Kubernetes(--log-dir)

Proposal

Add an event_log_dir field to the runtime: block in workflow YAML.

workflow:
  runtime:
    event_log_dir: ./logs

When omitted, behavior is unchanged($TMPDIR/conductor/).
Relative paths are resolved against the workflow file's directory.

Start at runtime configuration handling for the workflow.yaml runtime block and the always-on event log subscriber. Trace how the workflow file directory is available for relative paths; done means event_log_dir is accepted, defaults to $TMPDIR/conductor/, and resolves relative paths against the workflow file directory.