style: apply rustfmt across all crates and demos

Consistent formatting pass: line wrapping, import sorting, trailing
whitespace removal, let-chain indentation, merged derive attributes,
and unsafe block reformatting.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

crates/training/rtx-transformers/src/losses/cross_entropy.rs

@@ -44,7 +44,7 @@ pub struct CrossEntropyLoss {
 
 impl CrossEntropyLoss {
     /// Create a new cross-entropy loss with default configuration
-    #[must_use] 
+    #[must_use]
     pub fn new() -> Self {
         Self {
             config: CrossEntropyConfig::default(),
@@ -52,13 +52,13 @@ impl CrossEntropyLoss {
     }
 
     /// Create a new cross-entropy loss with custom configuration
-    #[must_use] 
+    #[must_use]
     pub fn with_config(config: CrossEntropyConfig) -> Self {
         Self { config }
     }
 
     /// Get the configuration
-    #[must_use] 
+    #[must_use]
     pub fn config(&self) -> &CrossEntropyConfig {
         &self.config
     }