TUI: display relative time for session updates in picker

Show "just now", "5m ago", "Yesterday" etc. instead of absolute timestamps
for better readability in the session picker list.

src/tui/tui-command-handlers.ts

@@ -39,6 +39,22 @@ type CommandHandlerContext = {
   formatSessionKey: (key: string) => string;
 };
 
+function formatRelativeTime(timestamp: number): string {
+  const now = Date.now();
+  const diff = now - timestamp;
+  const seconds = Math.floor(diff / 1000);
+  const minutes = Math.floor(seconds / 60);
+  const hours = Math.floor(minutes / 60);
+  const days = Math.floor(hours / 24);
+
+  if (seconds < 60) return "just now";
+  if (minutes < 60) return `${minutes}m ago`;
+  if (hours < 24) return `${hours}h ago`;
+  if (days === 1) return "Yesterday";
+  if (days < 7) return `${days}d ago`;
+  return new Date(timestamp).toLocaleDateString(undefined, { month: "short", day: "numeric" });
+}
+
 export function createCommandHandlers(context: CommandHandlerContext) {
   const {
     client,
@@ -147,7 +163,7 @@ export function createCommandHandlers(context: CommandHandlerContext) {
         return {
           value: session.key,
           label: title ? `${title} (${formattedKey})` : formattedKey,
-          description: session.updatedAt ? new Date(session.updatedAt).toLocaleString() : "",
+          description: session.updatedAt ? formatRelativeTime(session.updatedAt) : "",
           searchText: [
             session.displayName,
             session.label,