content: TOC rendering (toc.sx) + 8 tests (594/594)

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

lib/content/scoreboard.json

@@ -14,6 +14,7 @@
     "tree-edit": {"pass": 17, "fail": 0},
     "clone": {"pass": 10, "fail": 0},
     "query": {"pass": 13, "fail": 0},
+    "toc": {"pass": 8, "fail": 0},
     "transform": {"pass": 12, "fail": 0},
     "stats": {"pass": 17, "fail": 0},
     "table": {"pass": 15, "fail": 0},
@@ -29,7 +30,7 @@
     "md-doc": {"pass": 12, "fail": 0},
     "fed": {"pass": 20, "fail": 0}
   },
-  "total_pass": 586,
+  "total_pass": 594,
   "total_fail": 0,
-  "total": 586
+  "total": 594
 }