search: fuzzy matching via edit distance + 18 tests

editDist as an O(m*n) row-based Levenshtein DP (naive recursion is exponential
and times out under load); fuzzyTerms/fuzzyDocs/fuzzyRankTfIdf expand a term to
indexed terms within a max edit distance. 166/166.

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

lib/search/conformance.conf

@@ -26,6 +26,7 @@ PRELOADS=(
   lib/search/fed.sx
   lib/search/prefix.sx
   lib/search/page.sx
+  lib/search/fuzzy.sx
   lib/search/api.sx
   lib/search/testlib.sx
 )
@@ -38,4 +39,5 @@ SUITES=(
   "integration:lib/search/tests/integration.sx"
   "prefix:lib/search/tests/prefix.sx"
   "page:lib/search/tests/page.sx"
+  "fuzzy:lib/search/tests/fuzzy.sx"
 )