Add oneliner to case view

Introduce an `oneliner` field to the `CaseView` struct and update the
`scan_cases` function to read it from `oneliner.txt`. The `cases.html`
template is updated to display the oneliner if present. A new
integration test is added to verify the functionality.

server/src/routes/web.rs

@@ -22,6 +22,7 @@ struct CaseView {
     case_id_short: String,
     status: String,
     most_recent: String,
+    oneliner: Option<String>,
     recordings: Vec<RecordingView>,
 }
 
@@ -141,6 +142,11 @@ async fn scan_cases(data_path: &Path) -> Vec<CaseView> {
                     .map(|r| r.filename.clone())
                     .unwrap_or_default();
                 let case_id_short = case_id.chars().take(8).collect();
+                let oneliner = tokio::fs::read_to_string(case_entry.path().join("oneliner.txt"))
+                    .await
+                    .ok()
+                    .map(|s| s.trim().to_string())
+                    .filter(|s| !s.is_empty());
 
                 cases.push(CaseView {
                     user_slug: user_slug.clone(),
@@ -148,6 +154,7 @@ async fn scan_cases(data_path: &Path) -> Vec<CaseView> {
                     case_id_short,
                     status: status.to_string(),
                     most_recent,
+                    oneliner,
                     recordings,
                 });
             }