feat: make it possible to specify --config flags in the SDK

[bolinfest]

Updates the CodexOptions passed to the Codex() constructor in the SDK to support a config property that is a map of configuration data that will be transformed into --config flags passed to the invocation of codex.

Therefore, something like this:

const codex = new Codex({
  config: {
    show_raw_agent_reasoning: true,
    sandbox_workspace_write: { network_access: true },
  },
});

would result in the following args being added to the invocation of codex:

--config show_raw_agent_reasoning=true --config sandbox_workspace_write.network_access=true

[lopopolo-openai]

We should be able to provide a fully typed config interface and zod schema, including narrow enums of the permitted string literals in specific config positions. Can we push the model to do this?

For example, TypeScript can natively represent that sandbox has a fixed set of valid string literals values. Let's do that!

[lopopolo-openai]

Ideally with tests to ensure it matches the real config format!

[bolinfest]

That is not something we have the bandwidth to take on right now.