fix: use std::env::args_os instead of std::env::args (#1698)

Apparently `std::env::args()` will panic during iteration if any
argument to the process is not valid Unicode:

https://doc.rust-lang.org/std/env/fn.args.html

Let's avoid the risk and just go with `std::env::args_os()`.

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[//]: # (BEGIN SAPLING FOOTER)
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with [ReviewStack](https://reviewstack.dev/openai/codex/pull/1698).
* #1705
* #1703
* #1702
* __->__ #1698
* #1697

codex-rs/core/src/mcp_connection_manager.rs

@@ -8,6 +8,7 @@
 
 use std::collections::HashMap;
 use std::collections::HashSet;
+use std::ffi::OsString;
 use std::time::Duration;
 
 use anyhow::Context;
@@ -127,7 +128,12 @@ impl McpConnectionManager {
 
             join_set.spawn(async move {
                 let McpServerConfig { command, args, env } = cfg;
-                let client_res = McpClient::new_stdio_client(command, args, env).await;
+                let client_res = McpClient::new_stdio_client(
+                    command.into(),
+                    args.into_iter().map(OsString::from).collect(),
+                    env,
+                )
+                .await;
                 match client_res {
                     Ok(client) => {
                         // Initialize the client.