settings: Migration for fixing duplicated agent keys (#30237)

As a byproduct, this fixes bug where it's impossible to change Agent
profile

Closes #30000 

Release Notes:

- N/A

crates/migrator/src/migrator.rs

@@ -140,6 +140,10 @@ pub fn migrate_settings(text: &str) -> Result<Option<String>> {
             migrations::m_2025_05_05::SETTINGS_PATTERNS,
             &SETTINGS_QUERY_2025_05_05,
         ),
+        (
+            migrations::m_2025_05_08::SETTINGS_PATTERNS,
+            &SETTINGS_QUERY_2025_05_08,
+        ),
     ];
     run_migrations(text, migrations)
 }
@@ -230,6 +234,10 @@ define_query!(
     SETTINGS_QUERY_2025_05_05,
     migrations::m_2025_05_05::SETTINGS_PATTERNS
 );
+define_query!(
+    SETTINGS_QUERY_2025_05_08,
+    migrations::m_2025_05_08::SETTINGS_PATTERNS
+);
 
 // custom query
 static EDIT_PREDICTION_SETTINGS_MIGRATION_QUERY: LazyLock<Query> = LazyLock::new(|| {
@@ -743,4 +751,38 @@ mod tests {
             ),
         );
     }
+
+    #[test]
+    fn test_comment_duplicated_agent() {
+        assert_migrate_settings(
+            r#"{
+                "agent": {
+                    "name": "assistant-1",
+                "model": "gpt-4", // weird formatting
+                    "utf8": "привіт"
+                },
+                "something": "else",
+                "agent": {
+                    "name": "assistant-2",
+                    "model": "gemini-pro"
+                }
+            }
+        "#,
+            Some(
+                r#"{
+                /* Duplicated key auto-commented: "agent": {
+                    "name": "assistant-1",
+                "model": "gpt-4", // weird formatting
+                    "utf8": "привіт"
+                }, */
+                "something": "else",
+                "agent": {
+                    "name": "assistant-2",
+                    "model": "gemini-pro"
+                }
+            }
+        "#,
+            ),
+        );
+    }
 }