fix: resolve macOS build errors and warnings

Author: margbug01-cyber

Cargo.toml

@@ -42,7 +42,7 @@ windows = { version = "0.58", features = [
 
 # Unix-specific dependencies (macOS, Linux)
 [target.'cfg(unix)'.dependencies]
-nix = { version = "0.29", features = ["process", "signal", "fs"] }
+nix = { version = "0.29", features = ["process", "signal", "fs", "resource"] }
 libc = "0.2"
 
 [profile.release]

src/backend.rs

@@ -25,7 +25,6 @@ fn next_proxy_id() -> u64 {
 /// Backend instance state
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum BackendState {
-    Spawning,
     Ready,
     Stopping,
     Dead,

src/main.rs

@@ -78,8 +78,8 @@ impl Drop for SingleInstanceLock {
 
 #[cfg(unix)]
 fn acquire_single_instance_lock() -> Result<SingleInstanceLock> {
-    use nix::fcntl::{flock, FlockArg};
-    use std::os::unix::io::AsRawFd;
+    use nix::fcntl::{Flock, FlockArg};
+    use std::os::unix::io::AsFd;
 
     let lock_path = std::env::var("HOME")
         .map(|h| std::path::PathBuf::from(h).join(".mcp-proxy.lock"))
@@ -91,7 +91,7 @@ fn acquire_single_instance_lock() -> Result<SingleInstanceLock> {
         .mode(0o600)
         .open(&lock_path)?;
 
-    match flock(file.as_raw_fd(), FlockArg::LockExclusiveNonblock) {
+    match Flock::lock(file.as_fd().try_clone_to_owned()?, FlockArg::LockExclusiveNonblock) {
         Ok(_) => Ok(SingleInstanceLock { _file: file, path: lock_path }),
         Err(nix::errno::Errno::EWOULDBLOCK) => {
             anyhow::bail!("mcp-proxy is already running (lock file: {})", lock_path.display());