Add config to disable /feedback (#8909)

Some enterprises do not want their users to be able to `/feedback`.

<img width="395" height="325" alt="image"
src="https://github.com/user-attachments/assets/2dae9c0b-20c3-4a15-bcd3-0187857ebbd8"
/>

Adds to `config.toml`:

```toml
[feedback]
enabled = false
```

I've deliberately decided to:
1. leave other references to `/feedback` (e.g. in the interrupt message,
tips of the day) unchanged. I think we should continue to promote the
feature even if it is not usable currently.
2. leave the `/feedback` menu item selectable and display an error
saying it's disabled, rather than remove the menu item (which I believe
would raise more questions).

but happy to discuss these.

This will be followed by a change to requirements.toml that admins can
use to force the value of feedback.enabled.

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

@@ -356,6 +356,10 @@ pub struct Config {
     /// Defaults to `true`.
     pub analytics: bool,
 
+    /// When `false`, disables feedback collection across Codex product surfaces.
+    /// Defaults to `true`.
+    pub feedback_enabled: bool,
+
     /// OTEL configuration (exporter type, endpoint, headers, etc.).
     pub otel: crate::config::types::OtelConfig,
 }
@@ -820,6 +824,10 @@ pub struct ConfigToml {
     /// Defaults to `true`.
     pub analytics: Option<crate::config::types::AnalyticsConfigToml>,
 
+    /// When `false`, disables feedback collection across Codex product surfaces.
+    /// Defaults to `true`.
+    pub feedback: Option<crate::config::types::FeedbackConfigToml>,
+
     /// OTEL configuration.
     pub otel: Option<crate::config::types::OtelConfigToml>,
 
@@ -1403,6 +1411,11 @@ impl Config {
                 .and_then(|a| a.enabled)
                 .or(cfg.analytics.as_ref().and_then(|a| a.enabled))
                 .unwrap_or(true),
+            feedback_enabled: cfg
+                .feedback
+                .as_ref()
+                .and_then(|feedback| feedback.enabled)
+                .unwrap_or(true),
             tui_notifications: cfg
                 .tui
                 .as_ref()
@@ -1559,6 +1572,7 @@ mod tests {
     use crate::config::edit::ConfigEdit;
     use crate::config::edit::ConfigEditsBuilder;
     use crate::config::edit::apply_blocking;
+    use crate::config::types::FeedbackConfigToml;
     use crate::config::types::HistoryPersistence;
     use crate::config::types::McpServerTransportConfig;
     use crate::config::types::Notifications;
@@ -1885,6 +1899,25 @@ trust_level = "trusted"
         Ok(())
     }
 
+    #[test]
+    fn feedback_enabled_defaults_to_true() -> std::io::Result<()> {
+        let codex_home = TempDir::new()?;
+        let cfg = ConfigToml {
+            feedback: Some(FeedbackConfigToml::default()),
+            ..Default::default()
+        };
+
+        let config = Config::load_from_base_config_with_overrides(
+            cfg,
+            ConfigOverrides::default(),
+            codex_home.path().to_path_buf(),
+        )?;
+
+        assert_eq!(config.feedback_enabled, true);
+
+        Ok(())
+    }
+
     #[test]
     fn profile_legacy_toggles_override_base() -> std::io::Result<()> {
         let codex_home = TempDir::new()?;
@@ -3234,6 +3267,7 @@ model_verbosity = "high"
                 animations: true,
                 show_tooltips: true,
                 analytics: true,
+                feedback_enabled: true,
                 tui_scroll_events_per_tick: None,
                 tui_scroll_wheel_lines: None,
                 tui_scroll_trackpad_lines: None,
@@ -3318,6 +3352,7 @@ model_verbosity = "high"
             animations: true,
             show_tooltips: true,
             analytics: true,
+            feedback_enabled: true,
             tui_scroll_events_per_tick: None,
             tui_scroll_wheel_lines: None,
             tui_scroll_trackpad_lines: None,
@@ -3417,6 +3452,7 @@ model_verbosity = "high"
             animations: true,
             show_tooltips: true,
             analytics: false,
+            feedback_enabled: true,
             tui_scroll_events_per_tick: None,
             tui_scroll_wheel_lines: None,
             tui_scroll_trackpad_lines: None,
@@ -3502,6 +3538,7 @@ model_verbosity = "high"
             animations: true,
             show_tooltips: true,
             analytics: true,
+            feedback_enabled: true,
             tui_scroll_events_per_tick: None,
             tui_scroll_wheel_lines: None,
             tui_scroll_trackpad_lines: None,