Expose CODEX_HOME environment manager constructor

Make the environments.toml provider reachable from the exec-server crate API so the provider PR passes clippy before entrypoint wiring lands in the next stack PR.

Co-authored-by: Codex <noreply@openai.com>

codex-rs/exec-server/src/environment.rs

@@ -102,6 +102,30 @@ impl EnvironmentManager {
         Self::from_provider(&provider, local_runtime_paths).await
     }
 
+    /// Builds a manager from `CODEX_HOME` and local runtime paths used when
+    /// creating local filesystem helpers.
+    ///
+    /// If `CODEX_HOME/environments.toml` is present, it defines the configured
+    /// environments. Otherwise this preserves the legacy
+    /// `CODEX_EXEC_SERVER_URL` behavior. Callers that ignore user config
+    /// should use [`Self::from_env`] instead.
+    pub async fn from_codex_home(
+        codex_home: impl AsRef<std::path::Path>,
+        local_runtime_paths: ExecServerRuntimePaths,
+    ) -> Result<Self, ExecServerError> {
+        let provider = environment_provider_from_codex_home(codex_home.as_ref())?;
+        Self::from_provider(provider.as_ref(), local_runtime_paths).await
+    }
+
+    /// Builds a manager from the legacy environment-variable provider without
+    /// reading user config files from `CODEX_HOME`.
+    pub async fn from_env(
+        local_runtime_paths: ExecServerRuntimePaths,
+    ) -> Result<Self, ExecServerError> {
+        let provider = DefaultEnvironmentProvider::from_env();
+        Self::from_provider(&provider, local_runtime_paths).await
+    }
+
     async fn from_default_provider_url(
         exec_server_url: Option<String>,
         local_runtime_paths: ExecServerRuntimePaths,