content: plain-text render + excerpt (text.sx) + 20 tests (385/385)

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

lib/content/scoreboard.json

@@ -6,6 +6,7 @@
     "api": {"pass": 26, "fail": 0},
     "meta": {"pass": 27, "fail": 0},
     "markdown": {"pass": 20, "fail": 0},
+    "text": {"pass": 20, "fail": 0},
     "validate": {"pass": 17, "fail": 0},
     "store": {"pass": 29, "fail": 0},
     "snapshot": {"pass": 20, "fail": 0},
@@ -15,7 +16,7 @@
     "md-import": {"pass": 24, "fail": 0},
     "fed": {"pass": 20, "fail": 0}
   },
-  "total_pass": 365,
+  "total_pass": 385,
   "total_fail": 0,
-  "total": 365
+  "total": 385
 }