fix: public load_auth() fn always called with include_env_var=true (#1961)

Apparently `include_env_var=false` was only used for testing, so clean
up the API a little to make that clear.


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[//]: # (BEGIN SAPLING FOOTER)
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* #1962
* __->__ #1961

codex-rs/cli/src/login.rs

@@ -47,7 +47,7 @@ pub async fn run_login_with_api_key(
 pub async fn run_login_status(cli_config_overrides: CliConfigOverrides) -> ! {
     let config = load_config_or_exit(cli_config_overrides);
 
-    match load_auth(&config.codex_home, true) {
+    match load_auth(&config.codex_home) {
         Ok(Some(auth)) => match auth.mode {
             AuthMode::ApiKey => {
                 if let Some(api_key) = auth.api_key.as_deref() {

codex-rs/cli/src/proto.rs

@@ -36,7 +36,7 @@ pub async fn run_main(opts: ProtoCli) -> anyhow::Result<()> {
         .map_err(anyhow::Error::msg)?;
 
     let config = Config::load_with_cli_overrides(overrides_vec, ConfigOverrides::default())?;
-    let auth = load_auth(&config.codex_home, true)?;
+    let auth = load_auth(&config.codex_home)?;
     let ctrl_c = notify_on_sigint();
     let CodexSpawnOk { codex, .. } = Codex::spawn(config, auth, ctrl_c.clone()).await?;
     let codex = Arc::new(codex);