search: Phase 2 query AST + boolean/phrase eval + 28 tests

Query ADT (Term|And|Or|Not|Phrase) and evalQuery over docid-sorted posting
lists: boolean ops as linear merges, Not over the allDocs universe, Phrase via
positional adjacency. Batched both test suites into one program eval each
(search-batch) so they finish under heavy CPU load. 46/46.

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

lib/search/conformance.conf

@@ -20,10 +20,12 @@ PRELOADS=(
   lib/haskell/testlib.sx
   lib/search/tokenize.sx
   lib/search/index.sx
+  lib/search/query.sx
   lib/search/api.sx
   lib/search/testlib.sx
 )
 
 SUITES=(
   "index:lib/search/tests/index.sx"
+  "boolean:lib/search/tests/boolean.sx"
 )