search: Phase 2 query parser + 32 tests

Query tokenizer + recursive-descent parser: OR<AND<NOT precedence, implicit AND
on adjacency, quoted phrases, parens, case-insensitive keywords. parseQuery,
searchQuery, showQ. Worked around haskell-on-sx parser limits (ord-based
delimiters; multi-clause fns instead of []-pattern case alts). 78/78.

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

lib/search/api.sx

@@ -2,8 +2,15 @@
 ;; Tests and callers concatenate `search/src` with their own top-level bindings
 ;; (e.g. "result = lookupTerm \"cat\" idx\n") and evaluate via the haskell-on-sx
 ;; interpreter. Public Haskell entry points: indexDoc, lookupTerm, deleteDoc,
-;; docFreq, allTerms, tokens, positioned, evalQuery, parseQuery.
+;; docFreq, allTerms, tokens, positioned, evalQuery, parseQuery, searchQuery.
 
 (define
   search/src
-  (str search/tokenize-src "\n" search/index-src "\n" search/query-src))
+  (str
+    search/tokenize-src
+    "\n"
+    search/index-src
+    "\n"
+    search/query-src
+    "\n"
+    search/parse-src))