Fix summary: derive fail count so pass+warn+fail = total

Failed was only counting scored failures, missing unscored Pass tests.
Now computed as total - passed - warnings so segments always sum to total.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: MDA2AV

docs/static/probe/render.js

@@ -202,7 +202,7 @@ window.ProbeRender = (function () {
       var s = sv.summary;
       var total = s.total || 1;
       var warnings = s.warnings || 0;
-      var failed = s.failed || 0;
+      var failed = total - s.passed - warnings;
       var passPct = (s.passed / total) * 100;
       var warnPct = (warnings / total) * 100;
       var failPct = (failed / total) * 100;