feat: add reactive streaming and remove dead panel stream code

- Subscribe to StreamCascadeReactiveUpdates for real-time cascade state diffs
- Fall back to timer-based polling if streaming RPC unavailable
- Remove StreamCascadePanelReactiveUpdates code (dead end, only has plan_status/user_settings)
- Remove debug diff file-saving code
- Add stream_reactive_rpc() helper to backend

src/main.rs

@@ -53,6 +53,19 @@ struct Cli {
 
 #[tokio::main]
 async fn main() {
+    // Ignore SIGPIPE — prevents instant death when piped through tee/grep
+    #[cfg(unix)]
+    {
+        use tokio::signal::unix::{signal, SignalKind};
+        let mut sigpipe = signal(SignalKind::pipe()).expect("failed to install SIGPIPE handler");
+        tokio::spawn(async move {
+            loop {
+                sigpipe.recv().await;
+                // Silently ignore SIGPIPE
+            }
+        });
+    }
+
     // Install rustls CryptoProvider early — prevents panic under concurrent load
     let _ = rustls::crypto::ring::default_provider().install_default();
 
@@ -267,6 +280,7 @@ async fn main() {
     }
     // Remove stale MITM port file
     let _ = std::fs::remove_file(dirs_data_dir().join("mitm-port"));
+    eprintln!("  \x1b[1;32m✓ Server shutdown complete\x1b[0m\n");
     info!("Server shutdown complete");
 }
 
@@ -290,8 +304,14 @@ async fn shutdown_signal() {
     let terminate = std::future::pending::<()>();
 
     tokio::select! {
-        _ = ctrl_c => info!("Received SIGINT, shutting down..."),
-        _ = terminate => info!("Received SIGTERM, shutting down..."),
+        _ = ctrl_c => {
+            eprintln!("\n  \x1b[1;33m⚡ Shutting down gracefully...\x1b[0m");
+            info!("Received SIGINT, shutting down...");
+        },
+        _ = terminate => {
+            eprintln!("\n  \x1b[1;33m⚡ Received SIGTERM, shutting down...\x1b[0m");
+            info!("Received SIGTERM, shutting down...");
+        },
     }
 }