Update README screenshot with live dashboard capture

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Gregg Cochran

README.md

@@ -21,7 +21,7 @@ Then just type `agentpulse` — the dashboard opens in a new terminal window aut
 </div>
 
 <div align="center">
-<img src="assets/dashboard-screenshot.svg" alt="Agent Pulse Dashboard" width="700">
+<img src="assets/dashboard-screenshot.png" alt="Agent Pulse Dashboard" width="700">
 </div>
 
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