Add hostname to the configurable TUI status line (#39795)

## What changed

- Add `hostname` as a selectable status-line item and show it in setup previews.
- Read the normalized operating-system hostname without triggering DNS resolution, and omit the item when no hostname is available.

## Testing

- Cover hostname normalization, status-line rendering, and setup and surface previews.

GitOrigin-RevId: c5e4e0ee1dba6e4bfdf942562a6b037835ff9e69

codex-rs/config/src/host_name.rs

@@ -9,6 +9,10 @@ use winapi_util::sysinfo::ComputerNameKind;
 use winapi_util::sysinfo::get_computer_name;
 
 static HOST_NAME: LazyLock<Option<String>> = LazyLock::new(compute_host_name);
+static OS_HOST_NAME: LazyLock<Option<String>> = LazyLock::new(|| {
+    let kernel_hostname = gethostname::gethostname();
+    normalize_host_name(&kernel_hostname.to_string_lossy())
+});
 
 /// Returns a process-cached canonical hostname, falling back to the normalized
 /// kernel hostname. The first call on Unix may perform blocking DNS resolution.
@@ -16,9 +20,13 @@ pub fn host_name() -> Option<String> {
     HOST_NAME.clone()
 }
 
+/// Returns the process-cached operating-system hostname without DNS resolution.
+pub fn os_host_name() -> Option<String> {
+    OS_HOST_NAME.clone()
+}
+
 fn compute_host_name() -> Option<String> {
-    let kernel_hostname = gethostname::gethostname();
-    let kernel_hostname = normalize_host_name(&kernel_hostname.to_string_lossy())?;
+    let kernel_hostname = os_host_name()?;
 
     // Remote sandbox requirements are meant to target remote hosts by DNS name,
     // so prefer the canonical FQDN when the local resolver can provide one.
@@ -74,8 +82,20 @@ fn normalize_fqdn_candidate(hostname: &str) -> Option<String> {
 #[cfg(test)]
 mod tests {
     use super::normalize_fqdn_candidate;
+    use super::normalize_host_name;
+    use super::os_host_name;
     use pretty_assertions::assert_eq;
 
+    #[test]
+    fn os_host_name_matches_normalized_kernel_hostname() {
+        let kernel_hostname = gethostname::gethostname();
+
+        assert_eq!(
+            os_host_name(),
+            normalize_host_name(&kernel_hostname.to_string_lossy())
+        );
+    }
+
     #[test]
     fn normalize_fqdn_candidate_accepts_dns_qualified_name() {
         assert_eq!(

codex-rs/config/src/lib.rs

@@ -120,6 +120,7 @@ pub use hook_config::HooksToml;
 pub use hook_config::ManagedHooksRequirementsToml;
 pub use hook_config::MatcherGroup;
 pub use host_name::host_name;
+pub use host_name::os_host_name;
 pub use in_app_browser_requirements::InAppBrowserRequirementsToml;
 pub use marketplace_edit::MarketplaceConfigUpdate;
 pub use marketplace_edit::RemoveMarketplaceConfigOutcome;