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/scoreboard.json

@@ -1,10 +1,11 @@
 {
   "lang": "search",
-  "total_passed": 18,
+  "total_passed": 46,
   "total_failed": 0,
-  "total": 18,
+  "total": 46,
   "suites": [
-    {"name":"index","passed":18,"failed":0,"total":18}
+    {"name":"index","passed":18,"failed":0,"total":18},
+    {"name":"boolean","passed":28,"failed":0,"total":28}
   ],
-  "generated": "2026-06-06T18:12:50+00:00"
+  "generated": "2026-06-06T18:46:54+00:00"
 }