[Feature] Document hooks payload schema or expose codex session info --json for current model/reasoning effort

What variant of Codex are you using?

CLI

What feature would you like to see?

### Context

Codex CLI exposes per-turn structured spans in ~/.codex/log/codex-tui.log
including thread_id, model, and codex.turn.reasoning_effort. This
lets external tooling read current runtime config by filtering log
lines for the active thread.

This works as a workaround but would be cleaner with a documented API.

### Request — any one would help

1. Document the schema for ~/.codex/hooks.json events (current

~/.codex/config.toml shows features.codex_hooks = true, hooks
stable, but local install has no payload docs).

1. Expose codex session info --json for current model and

reasoning_effort, similar to other CLI introspection commands.

### Use case

Multi-agent session coordination tooling tracks declared vs actual
runtime config provenance. Codex runtime log parsing works today;
a supported API would reduce maintenance burden and avoid relying
on log line patterns that may change.

### Note

Not blocking — runtime-log parsing is a stable workaround. This is
about supported surface area, not unblocking critical functionality.

Additional information

_No response_