fix: use UTF-8 aware truncation in agent handlers to prevent panics

Author: Dario Yoshi

src/cortex-cli/src/agent_cmd/handlers/generate.rs

@@ -117,11 +117,11 @@ pub async fn run_generate(args: CreateArgs) -> Result<()> {
         println!("  {}", "-".repeat(36));
 
         // Show truncated prompt
-        let prompt_preview = if generated.system_prompt.len() > 500 {
+        let prompt_preview = if generated.system_prompt.chars().count() > 500 {
             format!(
                 "{}...\n\n    (truncated, {} chars total)",
-                &generated.system_prompt[..500],
-                generated.system_prompt.len()
+                generated.system_prompt.chars().take(500).collect::<String>(),
+                generated.system_prompt.chars().count()
             )
         } else {
             generated.system_prompt.clone()

src/cortex-cli/src/agent_cmd/handlers/list.rs

@@ -98,8 +98,8 @@ pub async fn run_list(args: ListArgs) -> Result<()> {
             .description
             .as_ref()
             .map(|d| {
-                if d.len() > 38 {
-                    format!("{}...", &d[..35])
+                if d.chars().count() > 38 {
+                    format!("{}...", d.chars().take(35).collect::<String>())
                 } else {
                     d.clone()
                 }

src/cortex-cli/src/agent_cmd/handlers/show.rs

@@ -136,11 +136,11 @@ pub async fn run_show(args: ShowArgs) -> Result<()> {
     if let Some(ref prompt) = agent.prompt {
         println!("\nSystem Prompt:");
         println!("{}", "-".repeat(40));
-        let preview = if prompt.len() > 500 {
+        let preview = if prompt.chars().count() > 500 {
             format!(
                 "{}...\n\n(truncated, {} chars total)",
-                &prompt[..500],
-                prompt.len()
+                prompt.chars().take(500).collect::<String>(),
+                prompt.chars().count()
             )
         } else {
             prompt.clone()