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/optimizers/mod.rs

@@ -89,7 +89,7 @@ pub struct BaseOptimizer {
 
 impl BaseOptimizer {
     /// Create a new base optimizer
-    #[must_use] 
+    #[must_use]
     pub fn new(learning_rate: f64) -> Self {
         Self {
             stored_gradients: HashMap::new(),
@@ -98,7 +98,7 @@ impl BaseOptimizer {
     }
 
     /// Get stored gradients
-    #[must_use] 
+    #[must_use]
     pub fn stored_gradients(&self) -> &HashMap<String, Tensor> {
         &self.stored_gradients
     }