This PR does the following: - divides user msgs into 3 categories: plain, user instructions, and environment context - Centralizes adding user instructions and environment context to a degree - Improve the integration testing Building on top of #3123 Specifically this [comment](https://github.com/openai/codex/pull/3123#discussion_r2319885089). We need to send the user message while ignoring the User Instructions and Environment Context we attach.
codex-protocol
This crate defines the "types" for the protocol used by Codex CLI, which includes both "internal types" for communication between codex-core and codex-tui, as well as "external types" used with codex mcp.
This crate should have minimal dependencies.
Ideally, we should avoid "material business logic" in this crate, as we can always introduce Ext-style traits to add functionality to types in other crates.