Persist local workspace side chats and add tab close controls (#60152)

## What changed

- Save side chats as attachments to their parent conversation when local workspace history supports them, and let users reopen them from the sidebar after a restart.
- Show chat names or first-prompt previews in sidebar labels, and allow saved side chats to be renamed with `/rename`.
- Add tab close buttons, middle-click closing, and the configurable `close_sidebar_tab` shortcut, defaulting to `Ctrl-X W`. Closing a saved chat keeps it available in the picker; archiving removes it from Side chats.
- Confirm actions that stop running work, discard unsent input, or lose temporary history. Delete saved TUI side chats when deleting their parent conversation.

## Testing

Add coverage for reopening saved side chats after restart, archive handling, close confirmations, and preventing close-confirmation keys from accepting a replacement approval dialog.

GitOrigin-RevId: 3d47533d007286a7354660c08df13a83dd48d5d7

codex-rs/config/src/tui_keymap.rs

@@ -145,6 +145,8 @@ pub struct TuiGlobalKeymap {
     pub focus_sidebar_tabs: Option<KeybindingsSpec>,
     /// Hide the focused sidebar pane.
     pub hide_pane: Option<KeybindingsSpec>,
+    /// Close the active sidebar tab.
+    pub close_sidebar_tab: Option<KeybindingsSpec>,
     /// Focus the parent conversation.
     pub focus_pane_left: Option<KeybindingsSpec>,
     /// Focus the open side conversation.