Clarify skill toggle summaries in the TUI (#57197)

## What changed

Omit zero-count actions and use singular or plural wording when summarizing skill changes. For example, show `Disabled 1 skill` instead of `0 skills enabled, 1 skills disabled`.

## Testing

Add a snapshot test covering enable-only, disable-only, mixed, and unchanged skill states, including no summary when nothing changes.

GitOrigin-RevId: ff68c799f29ceb8736e6941778d29a3f8d500b70

codex-rs/tui/src/chatwidget/skills.rs

@@ -130,10 +130,16 @@ impl ChatWidget {
         if enabled_count == 0 && disabled_count == 0 {
             return;
         }
-        self.add_info_message(
-            format!("{enabled_count} skills enabled, {disabled_count} skills disabled"),
-            /*hint*/ None,
-        );
+        let enabled_suffix = if enabled_count == 1 { "" } else { "s" };
+        let disabled_suffix = if disabled_count == 1 { "" } else { "s" };
+        let summary = match (enabled_count, disabled_count) {
+            (0, _) => format!("Disabled {disabled_count} skill{disabled_suffix}"),
+            (_, 0) => format!("Enabled {enabled_count} skill{enabled_suffix}"),
+            _ => format!(
+                "Enabled {enabled_count} skill{enabled_suffix}, disabled {disabled_count} skill{disabled_suffix}"
+            ),
+        };
+        self.add_info_message(summary, /*hint*/ None);
     }
 
     pub(crate) fn set_skills_from_response(&mut self, response: &SkillsListResponse) {

codex-rs/tui/src/chatwidget/snapshots/codex_tui__chatwidget__tests__manage_skills_summary.snap

@@ -0,0 +1,8 @@
+---
+source: tui/src/chatwidget/tests/skills_summary_tests.rs
+expression: "summaries.join(\"\\n\")"
+---
+enable: • Enabled 2 skills
+disable: • Disabled 1 skill
+mixed: • Enabled 2 skills, disabled 1 skill
+no changes:

codex-rs/tui/src/chatwidget/tests.rs

@@ -289,6 +289,8 @@ mod review_picker_tests;
 #[path = "tests/session_model_selection_tests.rs"]
 mod session_model_selection_tests;
 mod side;
+#[path = "tests/skills_summary_tests.rs"]
+mod skills_summary_tests;
 mod slash_commands;
 #[path = "tests/sparkle_submission_tests.rs"]
 mod sparkle_submission_tests;

codex-rs/tui/src/chatwidget/tests/skills_summary_tests.rs

@@ -0,0 +1,54 @@
+#![cfg(test)]
+
+//! Snapshots change-count wording and silence when skill state is unchanged.
+
+use super::*;
+
+#[tokio::test]
+async fn manage_skills_summary_snapshot() {
+    let (mut chat, mut rx, _ops) = make_chatwidget_manual(/*model_override*/ None).await;
+    let initial = [false, false, true];
+    chat.skills_all = initial
+        .iter()
+        .enumerate()
+        .map(|(index, &enabled)| SkillMetadata {
+            name: format!("skill-{index}"),
+            description: "Summary fixture".to_string(),
+            short_description: None,
+            interface: None,
+            dependencies: None,
+            path: test_path_buf(&format!("/tmp/skills/skill-{index}/SKILL.md"))
+                .abs()
+                .into(),
+            scope: crate::test_support::skill_scope_user(),
+            enabled,
+            plugin_id: None,
+        })
+        .collect();
+    drain_insert_history(&mut rx);
+    let mut summaries = Vec::new();
+    for (name, current) in [
+        ("enable", [true, true, true]),
+        ("disable", [false, false, false]),
+        ("mixed", [true, true, false]),
+        ("no changes", initial),
+    ] {
+        chat.skills_initial_state = Some(
+            chat.skills_all
+                .iter()
+                .zip(initial)
+                .map(|(skill, enabled)| (skill.path.to_inferred_path_uri().unwrap(), enabled))
+                .collect(),
+        );
+        for (skill, enabled) in chat.skills_all.iter_mut().zip(current) {
+            skill.enabled = enabled;
+        }
+        chat.handle_manage_skills_closed();
+        let lines = drain_insert_history(&mut rx).concat();
+        summaries.push(format!(
+            "{name}: {}",
+            lines_to_single_string(&lines).trim_end()
+        ));
+    }
+    assert_chatwidget_snapshot!("manage_skills_summary", summaries.join("\n"));
+}