perf(agent): use HashSet for eviction ID membership checks in consolidation

records.retain(|r| !evict_ids.contains(&r.id)) called Vec::contains
(linear scan) for every record against evict_ids, giving O(n·m) cost
on both Working- and Episodic-tier eviction every consolidation tick.
Build evict_ids as a HashSet for O(1) membership checks.

INT-15

crates/clawhdf5-agent/src/consolidation.rs

@@ -280,7 +280,7 @@ impl ConsolidationEngine {
         if working_count > capacity {
             let evict_n = working_count - capacity;
             // Collect the ids of the records to evict (lowest decay = first in sorted list).
-            let evict_ids: Vec<u64> = working_indices[..evict_n]
+            let evict_ids: std::collections::HashSet<u64> = working_indices[..evict_n]
                 .iter()
                 .map(|&i| self.records[i].id)
                 .collect();
@@ -341,7 +341,7 @@ impl ConsolidationEngine {
             });
 
             let evict_n = episodic_count - episodic_capacity;
-            let evict_ids: Vec<u64> = episodic_indices[..evict_n]
+            let evict_ids: std::collections::HashSet<u64> = episodic_indices[..evict_n]
                 .iter()
                 .map(|&i| self.records[i].id)
                 .collect();