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>

plans/search-on-sx.md

@@ -111,7 +111,8 @@ lib/search/index.sx                     lib/search/eval.sx
 ## Extensions (post-roadmap, search-shaped vocabulary)
 
 - [x] prefix / wildcard queries (`prefixTerms`, `prefixDocs`, `prefixRankTfIdf`) — 14 tests
-- [ ] fuzzy matching — edit distance term expansion
+- [x] fuzzy matching — edit distance term expansion (`editDist`, `fuzzyTerms`,
+  `fuzzyDocs`, `fuzzyRankTfIdf`) — 18 tests
 - [x] result pagination (offset / limit) — `paginate`, `pageTfIdf`, `pageBm25`,
   `resultCount` — 12 tests
 - [ ] snippet / highlight generation
@@ -119,6 +120,10 @@ lib/search/index.sx                     lib/search/eval.sx
 
 ## Progress log
 
+- **Extension: fuzzy matching (166/166 total).** Levenshtein `editDist` as an O(m*n)
+  row-based DP (the naive recursive version is exponential and times out under load),
+  `fuzzyTerms`/`fuzzyDocs`/`fuzzyRankTfIdf` expand a term to indexed terms within a max
+  edit distance. 18 tests.
 - **Extension: pagination (148/148 total).** `paginate off lim` windows a ranked list
   (take lim . drop off); `pageTfIdf`/`pageBm25` + `resultCount`. 12 tests. Note the
   full conformance now runs 8 suites sequentially and needs an overall timeout ~1900s