chore: ultra-clean artifacts (#13577)

See the readme

codex-rs/artifacts/README.md

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+# codex-artifacts
+
+Runtime and process-management helpers for Codex artifact generation.
+
+This crate has two main responsibilities:
+
+- locating, validating, and optionally downloading the pinned artifact runtime
+- spawning the artifact build or render command against that runtime
+
+## Module layout
+
+- `src/client.rs`
+  Runs build and render commands once a runtime has been resolved.
+- `src/runtime/manager.rs`
+  Defines the release locator and the package-manager-backed runtime installer.
+- `src/runtime/installed.rs`
+  Loads an extracted runtime from disk and validates its manifest and entrypoints.
+- `src/runtime/js_runtime.rs`
+  Chooses the JavaScript executable to use for artifact execution.
+- `src/runtime/manifest.rs`
+  Manifest types for release metadata and extracted runtimes.
+- `src/runtime/error.rs`
+  Public runtime-loading and installation errors.
+- `src/tests.rs`
+  Crate-level tests that exercise the public API and integration seams.
+
+## Public API
+
+- `ArtifactRuntimeManager`
+  Resolves or installs a runtime package into `~/.codex/packages/artifacts/...`.
+- `load_cached_runtime`
+  Reads a previously installed runtime from a caller-provided cache root without attempting a download.
+- `is_js_runtime_available`
+  Checks whether artifact execution is possible with either a cached runtime or a host JS runtime.
+- `ArtifactsClient`
+  Executes artifact build or render requests using either a managed or preinstalled runtime.