feat(embedding,notes): implement ADR-0056 Blake3 stable hashing and ADR-0057 priority-aware retention

server/src/handlers/notes.rs

@@ -108,7 +108,14 @@ impl McpTool for AddSessionSummaryHandler {
                 next_steps: req.next_steps.unwrap_or_default(),
             });
             if summaries.len() > 200 {
-                summaries.remove(0);
+                let now = crate::handlers::utils::now_secs();
+                if let Some((idx_to_remove, _)) = summaries.iter().enumerate().min_by_key(|(_, s)| {
+                    let is_expired = s.expires_at.map(|exp| exp < now).unwrap_or(false);
+                    let status_score = if is_expired { 0 } else { 1 };
+                    (status_score, s.timestamp)
+                }) {
+                    summaries.remove(idx_to_remove);
+                }
             }
         });
         Ok("Session summary added".to_string())