chore: Bump Rust version to 1.86 (#28021)

Closes #ISSUE

Release Notes:

- N/A

crates/prompt_store/src/prompts.rs

@@ -241,7 +241,11 @@ impl PromptBuilder {
 
     fn register_built_in_templates(handlebars: &mut Handlebars) -> Result<()> {
         for path in Assets.list("prompts")? {
-            if let Some(id) = path.split('/').last().and_then(|s| s.strip_suffix(".hbs")) {
+            if let Some(id) = path
+                .split('/')
+                .next_back()
+                .and_then(|s| s.strip_suffix(".hbs"))
+            {
                 if let Some(prompt) = Assets.load(path.as_ref()).log_err().flatten() {
                     log::debug!("Registering built-in prompt template: {}", id);
                     let prompt = String::from_utf8_lossy(prompt.as_ref());