Feature request: version marker (or stability guarantee) for the `codex exec --json` event schema — 0.144 "canonical turn items" silently broke downstream parsers

Context: I maintain Agent Console, a desktop console that runs Codex and Claude Code side by side. Multi-agent "room" sessions consume codex exec --json (thread.started / item.completed / turn.completed).

What happened: 0.144 restructured the event schema ("canonical turn items"). The change itself is fine — but there's no version marker in the stream and no schema changelog, so downstream parsers fail silently on upgrade instead of failing fast. Anyone consuming exec --json (CI integrations, wrappers, dashboards) has the same problem on every schema change.

Ask: one of:

1. a schema_version field in the first event of the stream (cheapest, unblocks everyone), or
2. --json-schema-version N flag with N frozen per major, or
3. if codex app-server is the intended stable surface for integrators, saying so explicitly in the docs would let us migrate deliberately instead of chasing TUI/CLI churn.

Happy to beta-test whichever direction you pick against a real multi-engine integration.

Start by tracing the codex exec --json event stream, including thread.started, item.completed, and turn.completed, and compare it with the codex app-server surface. Review the repository documentation for the supported integration contract. Done means one compatibility strategy is selected, documented, and usable by downstream parsers.