chore: extract validate_difficulty helper

clients/cli/src/main.rs

@@ -247,6 +247,18 @@ async fn main() -> Result<(), Box<dyn Error>> {
 /// * `check_mem` - Whether to check risky memory usage.
 /// * `with_background` - Whether to use the alternate TUI background color.
 /// * `max_tasks` - Optional maximum number of tasks to prove.
+
+fn validate_difficulty(difficulty_str: &str) -> Option<crate::nexus_orchestrator::TaskDifficulty> {
+    match difficulty_str.trim().to_ascii_uppercase().as_str() {
+        "SMALL" => Some(crate::nexus_orchestrator::TaskDifficulty::Small),
+        "SMALL_MEDIUM" => Some(crate::nexus_orchestrator::TaskDifficulty::SmallMedium),
+        "MEDIUM" => Some(crate::nexus_orchestrator::TaskDifficulty::Medium),
+        "LARGE" => Some(crate::nexus_orchestrator::TaskDifficulty::Large),
+        "EXTRA_LARGE" => Some(crate::nexus_orchestrator::TaskDifficulty::ExtraLarge),
+        _ => None,
+    }
+}
+
 /// * `show_mock_notification` - [Debug] Show rewards overlay on startup for testing.
 #[allow(clippy::too_many_arguments)]
 async fn start(
@@ -308,6 +320,7 @@ async fn start(
 
 #[cfg(test)]
 mod tests {
+    use super::validate_difficulty;
     use crate::nexus_orchestrator::TaskDifficulty;
 
     #[test]