docs: add recorded alert investigation walkthrough

pr-evidence/daily-issues/combined-demo/README.md

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+# Unified Issues demo
+
+Recorded at `afd8e32587c38e7c65247b7008070e0872fd70fc` on November 5, 2026. The 117-second video shows the current implementation, with five issue families in one inbox, key spend and provider latency investigations, model retirement and the existing Migration details page, Monitoring, and the notification bell
+
+The history is synthetic data in an isolated QA deployment. The real detector and projectors created the issues. A real gateway-backed request separately verified the request-tracking path. The Research agent key compares $100 with a $2 daily baseline, and 50,000 with 1,000 requests. Its Activity view contains 57,000 requests across October 28 through November 4. The provider case compares 2,400ms with 300ms across two models and two keys. The retirement date is a QA model configuration override, not a provider announcement
+
+The video joins two real browser recordings at the same commit and unchanged fixture state. No UI data or API responses were mocked. Desktop, dark and narrow views were checked. This is a demonstration of current behavior, not a production-readiness claim. Memory, serving-latency and authorization follow-ups remain tracked separately

pr-evidence/daily-issues/combined-demo/notification-proof.json

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+{
+  "source": "afd8e32587c38e7c65247b7008070e0872fd70fc",
+  "historical_input": "Explicit synthetic daily aggregates in isolated QA",
+  "notifications": [
+    {
+      "channel": "email",
+      "accepted": true,
+      "received_at": 1793864897.087595,
+      "path": "/ui/alerts",
+      "source_activity_link_verified": true
+    },
+    {
+      "channel": "slack",
+      "accepted": true,
+      "received_at": 1793864897.094204,
+      "path": "/ui/alerts",
+      "source_activity_link_verified": true
+    }
+  ],
+  "live_request_tracking": {
+    "requests": 1,
+    "timed_requests": 1
+  },
+  "replay_did_not_duplicate": true
+}