Quick polish pass on remaining screens; hide legacy chrome on RUM tab

Normalize radii, drop shadows/blur and font-black, and document the
one-view-at-a-time plan in AGENTS.md.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

otel-ui/src/App.tsx

@@ -73,7 +73,7 @@ function App() {
   // The Issues tab is the redesigned triage overview: it owns its own filter
   // bar and cards, so the legacy anomaly banner and volume waveform above it
   // would just duplicate that UI in a different visual language.
-  const isTriageOverview = activeTab === "tab0";
+  const isTriageOverview = activeTab === "tab0" || activeTab === "tab7";
 
   if (isCallback) {
     return <AuthCallbackView />;