fix(F1): silence unsafe_code warning on snapshot alloc — SAFETY comment + allow attribute

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/ml/src/cuda_pipeline/q_snapshot.rs

@@ -88,6 +88,9 @@ impl SnapshotRing {
 
         let n = self.param_count;
         let num_bytes = n * std::mem::size_of::<f32>();
+        // SAFETY: `alloc` returns uninitialized GPU memory, which we immediately
+        // overwrite with `memcpy_dtod` below before any read. No UB window.
+        #[allow(unsafe_code)]
         let mut new_weights = unsafe { self.stream.alloc::<f32>(n) }
             .map_err(|e| MLError::ModelError(format!("snapshot alloc: {e}")))?;
         {