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/tui/src/bottom_pane/snapshots/codex_tui__bottom_pane__status_line_setup__tests__setup_view_snapshot_includes_hostname.snap

@@ -0,0 +1,21 @@
+---
+source: tui/src/bottom_pane/status_line_setup.rs
+expression: "render_lines(&view,\n100).lines().map(str::trim_end).collect::<Vec<_>>().join(\"\\n\")"
+---
+
+  Configure Status Line
+  Select which items to display in the status line.
+
+  Type to search
+  >
+› [x] Use theme colors      Apply colors from the active /theme
+  ───────────────────────
+  [x] hostname              Current machine hostname (omitted when unavailable)
+  [x] current-dir           Current working directory
+  [ ] model                 Current model name
+  [ ] model-with-reasoning  Current model name with reasoning level
+  [ ] reasoning             Current reasoning level
+  [ ] project-name          Project name (omitted when unavailable)
+
+  ssh-build-01.example.com · ~/codex-rs
+  Press space to toggle; ←/→ to move; enter to confirm and close; esc to close

codex-rs/tui/src/bottom_pane/status_line_setup.rs

@@ -11,6 +11,7 @@
 //!
 //! - Model information (name, reasoning level)
 //! - Directory paths (current dir, project root)
+//! - Machine hostname
 //! - Git information (branch name)
 //! - Permissions profile
 //! - Approval mode
@@ -74,6 +75,9 @@ pub(crate) enum StatusLineItem {
     )]
     ProjectRoot,
 
+    /// Hostname of the machine running Codex.
+    Hostname,
+
     /// Current git branch name (if in a repository).
     GitBranch,
 
@@ -159,6 +163,7 @@ impl StatusLineItem {
             StatusLineItem::Reasoning => "Current reasoning level",
             StatusLineItem::CurrentDir => "Current working directory",
             StatusLineItem::ProjectRoot => "Project name (omitted when unavailable)",
+            StatusLineItem::Hostname => "Current machine hostname (omitted when unavailable)",
             StatusLineItem::GitBranch => "Current Git branch (omitted when unavailable)",
             StatusLineItem::PullRequestNumber => {
                 "Open pull request number for the current branch (omitted when unavailable)"
@@ -216,6 +221,7 @@ impl StatusLineItem {
             StatusLineItem::Reasoning => StatusSurfacePreviewItem::Reasoning,
             StatusLineItem::CurrentDir => StatusSurfacePreviewItem::CurrentDir,
             StatusLineItem::ProjectRoot => StatusSurfacePreviewItem::ProjectRoot,
+            StatusLineItem::Hostname => StatusSurfacePreviewItem::Hostname,
             StatusLineItem::GitBranch => StatusSurfacePreviewItem::GitBranch,
             StatusLineItem::PullRequestNumber => StatusSurfacePreviewItem::PullRequestNumber,
             StatusLineItem::BranchChanges => StatusSurfacePreviewItem::BranchChanges,
@@ -726,6 +732,38 @@ mod tests {
         assert_snapshot!(render_lines(&view, /*width*/ 100));
     }
 
+    #[test]
+    fn setup_view_snapshot_includes_hostname() {
+        let (tx_raw, _rx) = unbounded_channel::<AppEvent>();
+        let view = StatusLineSetupView::new(
+            Some(&[
+                StatusLineItem::Hostname.to_string(),
+                StatusLineItem::CurrentDir.to_string(),
+            ]),
+            /*use_theme_colors*/ true,
+            StatusSurfacePreviewData::from_iter([
+                (
+                    StatusLineItem::Hostname.preview_item(),
+                    "ssh-build-01.example.com".to_string(),
+                ),
+                (
+                    StatusLineItem::CurrentDir.preview_item(),
+                    "~/codex-rs".to_string(),
+                ),
+            ]),
+            AppEventSender::new(tx_raw),
+            crate::keymap::RuntimeKeymap::defaults().list,
+        );
+
+        assert_snapshot!(
+            render_lines(&view, /*width*/ 100)
+                .lines()
+                .map(str::trim_end)
+                .collect::<Vec<_>>()
+                .join("\n")
+        );
+    }
+
     fn render_lines(view: &StatusLineSetupView, width: u16) -> String {
         let height = view.desired_height(width);
         let area = Rect::new(0, 0, width, height);

codex-rs/tui/src/bottom_pane/status_line_style.rs

@@ -47,7 +47,9 @@ impl StatusLineAccent {
             | StatusLineItem::ThreadCredits
             | StatusLineItem::EstimatedThreadCost => Self::Usage,
             StatusLineItem::FiveHourLimit | StatusLineItem::WeeklyLimit => Self::Limit,
-            StatusLineItem::CodexVersion | StatusLineItem::SessionId => Self::Metadata,
+            StatusLineItem::CodexVersion | StatusLineItem::Hostname | StatusLineItem::SessionId => {
+                Self::Metadata
+            }
             StatusLineItem::FastMode | StatusLineItem::RawOutput => Self::Mode,
             StatusLineItem::Permissions => Self::Mode,
             StatusLineItem::ApprovalMode => Self::Mode,

codex-rs/tui/src/bottom_pane/status_surface_preview.rs

@@ -11,6 +11,7 @@ pub(crate) enum StatusSurfacePreviewItem {
     ProjectName,
     ProjectRoot,
     CurrentDir,
+    Hostname,
     Status,
     ThreadTitle,
     GitBranch,
@@ -46,6 +47,7 @@ impl StatusSurfacePreviewItem {
             StatusSurfacePreviewItem::ProjectName => "my-project",
             StatusSurfacePreviewItem::ProjectRoot => "my-project",
             StatusSurfacePreviewItem::CurrentDir => "~/my-project/subdir",
+            StatusSurfacePreviewItem::Hostname => "my-host",
             StatusSurfacePreviewItem::Status => "Working",
             StatusSurfacePreviewItem::ThreadTitle => "thread title",
             StatusSurfacePreviewItem::GitBranch => "feat/awesome-feature",
@@ -81,6 +83,7 @@ impl StatusSurfacePreviewItem {
             Self::ProjectName,
             Self::ProjectRoot,
             Self::CurrentDir,
+            Self::Hostname,
             Self::Status,
             Self::ThreadTitle,
             Self::GitBranch,