fix: force 4 tokio worker threads on node

.gitignore

@@ -220,7 +220,6 @@ proptest-regressions/
 
 # Package manager caches
 .cargo/
-!.cargo/config.toml
 
 # Claude/AI assistant files
 .claude/

src/bin/ant-node/main.rs

@@ -10,7 +10,14 @@ use tracing::{info, warn};
 use tracing_subscriber::prelude::*;
 use tracing_subscriber::{fmt, EnvFilter, Layer};
 
-#[tokio::main]
+/// Force at least 4 worker threads regardless of CPU count.
+///
+/// On small VMs (1-2 vCPU), the default `num_cpus` gives only 1-2 worker
+/// threads.  The NAT traversal `poll()` function does synchronous work
+/// (`parking_lot` locks, `DashMap` iteration) that blocks its worker thread.
+/// With only 1 worker, this freezes the entire runtime — timers stop,
+/// keepalives can't fire, and connections die silently.
+#[tokio::main(flavor = "multi_thread", worker_threads = 4)]
 async fn main() -> color_eyre::Result<()> {
     // Initialize error handling
     color_eyre::install()?;