Add 6-hour [aw] failure investigation workflow (#26694)

Author: Copilot

.github/mcp.json

@@ -0,0 +1,8 @@
+{
+  "mcpServers": {
+    "github-agentic-workflows": {
+      "command": "gh",
+      "args": ["aw", "mcp-server"]
+    }
+  }
+}