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/conformance.conf

@@ -0,0 +1,29 @@
+# search-on-sx conformance config — sourced by lib/guest/conformance.sh.
+
+LANG_NAME=search
+SCOREBOARD_DIR=lib/search
+MODE=counters
+COUNTERS_PASS=hk-test-pass
+COUNTERS_FAIL=hk-test-fail
+TIMEOUT_PER_SUITE=600
+
+PRELOADS=(
+  lib/haskell/tokenizer.sx
+  lib/haskell/layout.sx
+  lib/haskell/parser.sx
+  lib/haskell/desugar.sx
+  lib/haskell/runtime.sx
+  lib/haskell/match.sx
+  lib/haskell/eval.sx
+  lib/haskell/map.sx
+  lib/haskell/set.sx
+  lib/haskell/testlib.sx
+  lib/search/tokenize.sx
+  lib/search/index.sx
+  lib/search/api.sx
+  lib/search/testlib.sx
+)
+
+SUITES=(
+  "index:lib/search/tests/index.sx"
+)