Add an agents overview dashboard to the TUI (#39094)

## What changed

- Add `/agents` to open a full-screen dashboard of loaded root sessions from the shared app server, with subagent status reflected in each root session.
- Support search, navigation, and grouping sessions by project or status.
- Refresh the dashboard when relevant thread notifications arrive, while preserving its selection and view preferences.
- Show a clear message when the dashboard is unavailable with the embedded app server.

## Testing

- Add coverage for dashboard rendering, status grouping, persisted view state, and restoring the conversation viewport after closing the dashboard.
- Cover `/agents` command discovery and dispatch from parent-owned threads.

GitOrigin-RevId: 6651f4c47358116e1809da3ac8844a5842026a95

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

@@ -384,6 +384,7 @@ fn parent_owned_command_is_allowed(command: SlashCommand, args: &str) -> bool {
                 | SlashCommand::App
                 | SlashCommand::Side
                 | SlashCommand::Btw
+                | SlashCommand::Agents
                 | SlashCommand::MultiAgents
                 | SlashCommand::Vim
                 | SlashCommand::Keymap
@@ -4976,6 +4977,7 @@ mod tests {
     #[test]
     fn parent_owned_thread_allows_bare_navigation_commands() {
         for (command, expected) in [
+            ("/agents", SlashCommand::Agents),
             ("/subagents", SlashCommand::MultiAgents),
             ("/side", SlashCommand::Side),
             ("/btw", SlashCommand::Btw),
@@ -4996,13 +4998,13 @@ mod tests {
     fn parent_owned_thread_allows_safe_command_selected_from_prefix() {
         let (mut composer, _rx) = new_test_composer();
         composer.set_parent_owned_thread();
-        type_chars_humanlike(&mut composer, &['/', 's', 'u', 'b']);
+        type_chars_humanlike(&mut composer, &['/', 'a', 'g']);
 
         let result = composer
             .handle_key_event(KeyEvent::new(KeyCode::Enter, KeyModifiers::NONE))
             .0;
 
-        assert_eq!(result, InputResult::Command(SlashCommand::MultiAgents));
+        assert_eq!(result, InputResult::Command(SlashCommand::Agents));
     }
 
     #[test]

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

@@ -1222,6 +1222,21 @@ impl BottomPane {
         popup_consts::standard_popup_hint_line_for_keymap(&self.keymap.list)
     }
 
+    pub(crate) fn replace_view_if_present(
+        &mut self,
+        view_id: &'static str,
+        view: Box<dyn BottomPaneView>,
+    ) {
+        if let Some(index) = self
+            .view_stack
+            .iter()
+            .rposition(|existing| existing.view_id() == Some(view_id))
+        {
+            self.view_stack[index] = view;
+            self.request_redraw();
+        }
+    }
+
     pub(crate) fn list_keymap(&self) -> crate::keymap::ListKeymap {
         self.keymap.list.clone()
     }
@@ -1383,7 +1398,7 @@ impl BottomPane {
             .lines()
             .next()
             .and_then(parse_slash_name)
-            .is_some_and(|(name, _, _)| name == "subagents");
+            .is_some_and(|(name, _, _)| matches!(name, "agents" | "subagents"));
 
         self.keymap.chat.interrupt_turn.is_pressed(key_event)
             && self.is_task_running

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

@@ -303,6 +303,7 @@ mod tests {
             commands,
             vec![
                 SlashCommand::Ide,
+                SlashCommand::Agents,
                 SlashCommand::Copy,
                 SlashCommand::Export,
                 SlashCommand::Raw,

codex-rs/tui/src/bottom_pane/snapshots/codex_tui__bottom_pane__command_popup__tests__command_popup_default_items.snap

@@ -23,6 +23,7 @@ expression: commands
 /app - continue this session in the Desktop app
 /init - create an AGENTS.md file with instructions for Codex
 /compact - summarize conversation to prevent hitting the context limit
+/agents - view and switch between all active agent sessions
 /side - start a side conversation in an ephemeral fork
 /copy - copy last response as markdown
 /export - export the conversation as markdown