search: boolean-filtered ranked search + 11 tests

searchRankTfIdf/searchRankBm25 parse a boolean query, filter docs via evalQuery,
then rank survivors by relevance over the query's leaf terms (queryTerms) — the
filter-then-rank pattern. 225/225.

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

lib/search/conformance.conf

@@ -31,6 +31,7 @@ PRELOADS=(
   lib/search/stem.sx
   lib/search/near.sx
   lib/search/syn.sx
+  lib/search/rankq.sx
   lib/search/api.sx
   lib/search/testlib.sx
 )
@@ -48,4 +49,5 @@ SUITES=(
   "stem:lib/search/tests/stem.sx"
   "near:lib/search/tests/near.sx"
   "syn:lib/search/tests/syn.sx"
+  "rankq:lib/search/tests/rankq.sx"
 )