search: Phase 1 tokenizer + inverted index + 18 tests

Tokenizer (lowercase, strip punctuation, positions) and a sorted assoc-list
inverted index [(Term,[(DocId,[Pos])])] with indexDoc/deleteDoc/lookupTerm/
docFreq/allTerms. Search lib is haskell-on-sx source assembled into search/src;
tests reuse hk-test counters via a search-eval helper. conformance.sh models
lib/haskell.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/search/scoreboard.json

@@ -0,0 +1,10 @@
+{
+  "lang": "search",
+  "total_passed": 18,
+  "total_failed": 0,
+  "total": 18,
+  "suites": [
+    {"name":"index","passed":18,"failed":0,"total":18}
+  ],
+  "generated": "2026-06-06T18:12:50+00:00"
+}