feat(ml): export GPU types in prelude

Add DeviceConfig and GpuCapabilities re-exports to ml::prelude so
downstream crates can import GPU management types via a single
`use ml::prelude::*` statement.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ml/src/lib.rs

@@ -1950,6 +1950,9 @@ pub mod prelude {
     // Constants
     pub use crate::{MAX_INFERENCE_LATENCY_US, PRECISION_FACTOR};
 
+    // GPU device management
+    pub use crate::gpu::{capabilities::GpuCapabilities, DeviceConfig};
+
     // Tensor types from candle
     pub use candle_core::{Device, Tensor};
     pub use candle_nn::{Module, VarBuilder, VarMap};