fix(devtools): package Codex daemon and use upstream Pi

packages/codex.md

@@ -0,0 +1,39 @@
+# Local Codex package adapter
+
+`codex.nix` adds the complete package layout required by Codex daemon startup.
+The pinned Numtide package supplies binaries but lacks the manifest and bundled
+ripgrep. The adapter copies the binaries without rebuilding Rust.
+
+Remove this adapter and select `llmPkgs.codex` when Numtide supplies the complete
+layout. Also remove the custom package export and adjust the flake check.
+
+## Validation
+
+Build the package and run its layout checks:
+
+```sh
+nix build .#codex
+```
+
+Test daemon provisioning outside the Nix sandbox:
+
+```sh
+python3 packages/codex-daemon-test.py ./result/bin/codex
+```
+
+The daemon test uses a temporary `CODEX_HOME`, disables automatic updates there,
+and stops the test daemon. It does not use your normal Codex sessions or settings.
+
+## Runtime limits
+
+Codex copies the package into `~/.codex/packages/app-server-daemon`.
+The copied Nix binaries still reference dependencies in `/nix/store`.
+Keep the corresponding Nix system generation while using that daemon version.
+After a Nix upgrade, `codex app-server daemon update --help` describes how to
+select the current CLI package with `--from-cli`.
+
+The adapter does not change your daemon update settings. Codex can automatically
+update its private daemon independently of the CLI installed by Nix.
+
+Only aarch64-darwin daemon startup has been tested locally. The derivation also
+provides the required bubblewrap executable on Linux.