improve lexical warmup and standardize stopword pipeline

modules/story-summary/vector/utils/stopwords-patch.js

@@ -0,0 +1,9 @@
+// Small domain-level tuning surface.
+// Keep this file tiny: add/remove only words that are repeatedly noisy in real logs.
+
+// Extra stopwords on top of BASE_STOP_WORDS.
+export const DOMAIN_STOP_WORDS = [];
+
+// High-value words that must never be filtered as stopwords.
+// Default to empty for plugin-wide deployment; entity names are already protected dynamically.
+export const KEEP_WORDS = [];