feat(core): add command, intent, and routing primitives

src/session/indexer.ts

@@ -0,0 +1,48 @@
+export interface HistoryMetadata {
+  keywords: string[];
+  topics: string[];
+}
+
+export interface HistoryIndexerConfig {
+  maxKeywords: number;
+}
+
+const STOPWORDS = new Set([
+  'a', 'an', 'and', 'are', 'as', 'at', 'be', 'by', 'for', 'from', 'has', 'he', 'in', 'is', 'it', 'its',
+  'of', 'on', 'or', 'that', 'the', 'to', 'was', 'were', 'will', 'with', 'you', 'your', 'we', 'this',
+  'they', 'their', 'our', 'but', 'not', 'can', 'just', 'into', 'about', 'after', 'before', 'than', 'then',
+]);
+
+export function tokenize(text: string): string[] {
+  return text
+    .toLowerCase()
+    .split(/[^a-z0-9]+/)
+    .filter(token => token.length >= 3 && !STOPWORDS.has(token));
+}
+
+export class SessionIndexer {
+  private readonly maxKeywords: number;
+
+  constructor(config: HistoryIndexerConfig) {
+    this.maxKeywords = config.maxKeywords;
+  }
+
+  indexText(text: string): HistoryMetadata {
+    const tokens = tokenize(text);
+    const frequencies = new Map<string, number>();
+
+    for (const token of tokens) {
+      frequencies.set(token, (frequencies.get(token) ?? 0) + 1);
+    }
+
+    const sorted = Array.from(frequencies.entries())
+      .sort((a, b) => b[1] - a[1] || a[0].localeCompare(b[0]))
+      .slice(0, this.maxKeywords)
+      .map(([token]) => token);
+
+    return {
+      keywords: sorted,
+      topics: sorted.slice(0, Math.min(3, sorted.length)),
+    };
+  }
+}