feat(tui): add /statusline command for interactive status line configuration (#10546)

## Summary
- Adds a new `/statusline` command to configure TUI footer status line
- Introduces reusable `MultiSelectPicker` component with keyboard
navigation, optional ordering and toggle support
- Implement status line setup modal that persist configuration to
config.toml

  ## Status Line Items
  The following items can be displayed in the status line:
  - **Model**: Current model name (with optional reasoning level)
  - **Context**: Remaining/used context window percentage
  - **Rate Limits**: 5-day and weekly usage limits
  - **Git**: Current branch (with optimized lookups)
  - **Tokens**: Used tokens, input/output token counts
  - **Session**: Session ID (full or shortened prefix)
  - **Paths**: Current directory, project root
  - **Version**: Codex version

  ## Features
  - Live preview while configuring status line items
  - Fuzzy search filtering in the picker
  - Intelligent truncation when items don't fit
  - Items gracefully omit when data is unavailable
  - Configuration persists to `config.toml`
  - Validates and warns about invalid status line items

  ## Test plan
  - [x] Run `/statusline` and verify picker UI appears
  - [x] Toggle items on/off and verify live preview updates
  - [x] Confirm selection persists after restart
  - [x] Verify truncation behavior with many items selected
  - [x] Test git branch detection in and out of git repos

---------

Co-authored-by: Josh McKinney <joshka@openai.com>

codex-rs/core/src/config/mod.rs

@@ -224,6 +224,9 @@ pub struct Config {
     /// - `never`: Never use alternate screen (inline mode, preserves scrollback).
     pub tui_alternate_screen: AltScreenMode,
 
+    /// Ordered list of status line item identifiers for the TUI.
+    pub tui_status_line: Option<Vec<String>>,
+
     /// The directory that should be treated as the current working directory
     /// for the session. All relative paths inside the business-logic layer are
     /// resolved against this path.
@@ -1712,6 +1715,7 @@ impl Config {
                 .as_ref()
                 .map(|t| t.alternate_screen)
                 .unwrap_or_default(),
+            tui_status_line: cfg.tui.as_ref().and_then(|t| t.status_line.clone()),
             otel: {
                 let t: OtelConfigToml = cfg.otel.unwrap_or_default();
                 let log_user_prompt = t.log_user_prompt.unwrap_or(false);
@@ -1947,6 +1951,7 @@ persistence = "none"
                 show_tooltips: true,
                 experimental_mode: None,
                 alternate_screen: AltScreenMode::Auto,
+                status_line: None,
             }
         );
     }
@@ -3897,6 +3902,7 @@ model_verbosity = "high"
                 analytics_enabled: Some(true),
                 feedback_enabled: true,
                 tui_alternate_screen: AltScreenMode::Auto,
+                tui_status_line: None,
                 otel: OtelConfig::default(),
             },
             o3_profile_config
@@ -3983,6 +3989,7 @@ model_verbosity = "high"
             analytics_enabled: Some(true),
             feedback_enabled: true,
             tui_alternate_screen: AltScreenMode::Auto,
+            tui_status_line: None,
             otel: OtelConfig::default(),
         };
 
@@ -4084,6 +4091,7 @@ model_verbosity = "high"
             analytics_enabled: Some(false),
             feedback_enabled: true,
             tui_alternate_screen: AltScreenMode::Auto,
+            tui_status_line: None,
             otel: OtelConfig::default(),
         };
 
@@ -4171,6 +4179,7 @@ model_verbosity = "high"
             analytics_enabled: Some(true),
             feedback_enabled: true,
             tui_alternate_screen: AltScreenMode::Auto,
+            tui_status_line: None,
             otel: OtelConfig::default(),
         };