improve lexical warmup and standardize stopword pipeline

modules/story-summary/vector/retrieval/metrics.js

@@ -52,6 +52,10 @@ export function createMetrics() {
             eventHits: 0,
             searchTime: 0,
             indexReadyTime: 0,
+            idfEnabled: false,
+            idfDocCount: 0,
+            topIdfTerms: [],
+            termSearches: 0,
             eventFilteredByDense: 0,
             floorFilteredByDense: 0,
         },
@@ -274,6 +278,20 @@ export function formatMetricsLog(metrics) {
     if (m.lexical.indexReadyTime > 0) {
         lines.push(`├─ index_ready_time: ${m.lexical.indexReadyTime}ms`);
     }
+    lines.push(`├─ idf_enabled: ${!!m.lexical.idfEnabled}`);
+    if (m.lexical.idfDocCount > 0) {
+        lines.push(`├─ idf_doc_count: ${m.lexical.idfDocCount}`);
+    }
+    if ((m.lexical.topIdfTerms || []).length > 0) {
+        const topIdfText = m.lexical.topIdfTerms
+            .slice(0, 5)
+            .map(x => `${x.term}:${x.idf}`)
+            .join(', ');
+        lines.push(`├─ top_idf_terms: [${topIdfText}]`);
+    }
+    if (m.lexical.termSearches > 0) {
+        lines.push(`├─ term_searches: ${m.lexical.termSearches}`);
+    }
     if (m.lexical.eventFilteredByDense > 0) {
         lines.push(`├─ event_filtered_by_dense: ${m.lexical.eventFilteredByDense}`);
     }