Fix warn macro import for Linux build, add cargo PATH to release script

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

release.sh

@@ -1,6 +1,9 @@
 #!/usr/bin/env bash
 set -euo pipefail
 
+# Ensure cargo is on PATH
+export PATH="${HOME}/.cargo/bin:${PATH}"
+
 # ============================================================
 # Release configuration
 # ============================================================

src/ipc.rs

@@ -2,7 +2,7 @@ use anyhow::{Context, Result};
 use serde::{Deserialize, Serialize};
 use std::io::{Read, Write};
 use std::sync::Arc;
-use tracing::{debug, info};
+use tracing::{debug, info, warn};
 
 use crate::shared_state::SharedState;