feat(tui): add usage overlay and sidebar for displaying usage statistics and tasks

feat(tui): implement status bar with connection and turn state indicators
feat(tui): create workflow panel for agent status and progress visualization
feat(web): introduce web frontend interface with static file serving
feat(ws): add WebSocket interface for real-time communication and session management

apps/infrastructure/src/review/staleness.rs

@@ -0,0 +1,15 @@
+//! Staleness detection for lesson cache entries.
+
+use std::time::{SystemTime, UNIX_EPOCH};
+
+/// How long (in seconds) before a lesson is considered stale.
+const STALE_THRESHOLD_SECS: u64 = 86400 * 7; // 7 days
+
+/// Check whether a lesson timestamp is stale.
+pub fn is_stale(updated_at: i64) -> bool {
+    let now = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs() as i64;
+    now.saturating_sub(updated_at) > STALE_THRESHOLD_SECS as i64
+}