Support remote SAM3 inference through a private Metal worker

crates/segment/src/bin/lightcraft-sam3-worker.rs

@@ -0,0 +1,8 @@
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let mut args = std::env::args().skip(1);
+    let dir = args.next().ok_or("usage: lightcraft-sam3-worker MODEL_DIR [127.0.0.1:8793]")?;
+    let address = args.next().unwrap_or_else(|| "127.0.0.1:8793".into()).parse()?;
+    let device = candle_core::Device::new_metal(0)?;
+    lightcraft_segment::remote::serve(address, std::path::Path::new(&dir), device)?;
+    Ok(())
+}