Add opt-out for rate limit model nudge (#6433)

## Summary
- add a `hide_rate_limit_model_nudge` notice flag plus config edit
plumbing so the rate limit reminder preference is persisted and
documented
- extend the chat widget prompt with a "never show again" option, and
wire new app events so selecting it hides future nudges immediately and
writes the config
- add unit coverage and refresh the snapshot for the three-option prompt

## Testing
- `just fmt`
- `just fix -p codex-tui`
- `just fix -p codex-core`
- `cargo test -p codex-tui`
- `cargo test -p codex-core` *(fails at
`exec::tests::kill_child_process_group_kills_grandchildren_on_timeout`:
grandchild process still alive)*

------
[Codex
Task](https://chatgpt.com/codex/tasks/task_i_6910d7f407748321b2661fc355416994)

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

@@ -25,6 +25,8 @@ pub enum ConfigEdit {
     SetNoticeHideFullAccessWarning(bool),
     /// Toggle the Windows world-writable directories warning acknowledgement flag.
     SetNoticeHideWorldWritableWarning(bool),
+    /// Toggle the rate limit model nudge acknowledgement flag.
+    SetNoticeHideRateLimitModelNudge(bool),
     /// Toggle the Windows onboarding acknowledgement flag.
     SetWindowsWslSetupAcknowledged(bool),
     /// Replace the entire `[mcp_servers]` table.
@@ -246,6 +248,11 @@ impl ConfigDocument {
                 &[Notice::TABLE_KEY, "hide_world_writable_warning"],
                 value(*acknowledged),
             )),
+            ConfigEdit::SetNoticeHideRateLimitModelNudge(acknowledged) => Ok(self.write_value(
+                Scope::Global,
+                &[Notice::TABLE_KEY, "hide_rate_limit_model_nudge"],
+                value(*acknowledged),
+            )),
             ConfigEdit::SetWindowsWslSetupAcknowledged(acknowledged) => Ok(self.write_value(
                 Scope::Global,
                 &["windows_wsl_setup_acknowledged"],
@@ -486,6 +493,12 @@ impl ConfigEditsBuilder {
         self
     }
 
+    pub fn set_hide_rate_limit_model_nudge(mut self, acknowledged: bool) -> Self {
+        self.edits
+            .push(ConfigEdit::SetNoticeHideRateLimitModelNudge(acknowledged));
+        self
+    }
+
     pub fn set_windows_wsl_setup_acknowledged(mut self, acknowledged: bool) -> Self {
         self.edits
             .push(ConfigEdit::SetWindowsWslSetupAcknowledged(acknowledged));
@@ -733,6 +746,34 @@ hide_full_access_warning = true
         assert_eq!(contents, expected);
     }
 
+    #[test]
+    fn blocking_set_hide_rate_limit_model_nudge_preserves_table() {
+        let tmp = tempdir().expect("tmpdir");
+        let codex_home = tmp.path();
+        std::fs::write(
+            codex_home.join(CONFIG_TOML_FILE),
+            r#"[notice]
+existing = "value"
+"#,
+        )
+        .expect("seed");
+
+        apply_blocking(
+            codex_home,
+            None,
+            &[ConfigEdit::SetNoticeHideRateLimitModelNudge(true)],
+        )
+        .expect("persist");
+
+        let contents =
+            std::fs::read_to_string(codex_home.join(CONFIG_TOML_FILE)).expect("read config");
+        let expected = r#"[notice]
+existing = "value"
+hide_rate_limit_model_nudge = true
+"#;
+        assert_eq!(contents, expected);
+    }
+
     #[test]
     fn blocking_replace_mcp_servers_round_trips() {
         let tmp = tempdir().expect("tmpdir");

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

@@ -360,6 +360,8 @@ pub struct Notice {
     pub hide_full_access_warning: Option<bool>,
     /// Tracks whether the user has acknowledged the Windows world-writable directories warning.
     pub hide_world_writable_warning: Option<bool>,
+    /// Tracks whether the user opted out of the rate limit model switch reminder.
+    pub hide_rate_limit_model_nudge: Option<bool>,
 }
 
 impl Notice {