refactor(semantle,doantu): drop ConceptNet vestiges, trim wordlist API

Now that both modules run on Workers AI embeddings, drop the legacy
Word2SimError alias, the unused wordlist helpers (getLine, LINE_COUNT,
pickFromPool), and every comment/README section still describing the
removed ConceptNet backend. Fix the bge-small doc typo in semantle/index.js
and align the semantle api-client test fake-vector dim with the real
384-dim output.

scripts/build-semantle-words.js

@@ -31,7 +31,7 @@ if (!res.ok) throw new Error(`fetch failed: ${res.status} ${res.statusText}`);
 const text = await res.text();
 
 // Normalize only: trim whitespace, lowercase, drop blanks, dedupe.
-// Preserve original frequency order so `getLine(n)` stays a frequency rank.
+// Preserve original frequency order — source is ranked by Google Ngram.
 const words = Array.from(
   new Set(
     text