docs(webapp): add .server-changes entry for mollifier dashboard

Dashboard PR is webapp-only with no public-package changes, so per
.claude/rules/server-apps.md it needs a .server-changes/ entry (the
buffer PR uses a changeset because it touches packages/redis-worker).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: d-cs

.server-changes/mollifier-dashboard.md

@@ -0,0 +1,6 @@
+---
+area: webapp
+type: feature
+---
+
+Mollifier dashboard surface: run-detail page renders buffered runs via synthetic trace, header, and span shapes; admin-only "Buffered" indicator and drainer LOG event in the trace tree.