⚡ Optimize RichardsGlu::compute_gradients by removing unnecessary clones

[google-labs-jules]

This PR optimizes RichardsGlu::compute_gradients by eliminating unnecessary Array2 cloning operations when using cached values.

💡 What:

• Modified src/richards/richards_glu.rs to use a conditional borrowing pattern. Instead of cloning the cached Option<Array2<f32>>, the code now borrows the cached reference if available, or creates a new owned array (stored in a local variable) and borrows it if not.
• Updated variable usages to work with &Array2<f32> references.
• Added a new benchmark richards_glu_bench to verify performance.

🎯 Why:

• The previous implementation used .cloned().unwrap_or_else(...), which forced a full matrix copy even when the cache was present. This caused significant allocation and memory copy overhead during training.

📊 Measured Improvement:

• Baseline: ~31.46 ms
• Optimized: ~29.13 ms
• Improvement: ~7.4% reduction in execution time for compute_gradients.

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PR created automatically by Jules for task 4074737496829598444 started by @ryancinsight

High-level PR Summary

This PR optimizes the compute_gradients method in RichardsGlu by replacing expensive cloning operations with conditional borrowing. Instead of cloning cached Array2<f32> matrices using cloned().unwrap_or_else(...), the code now uses a pattern that borrows cached references when available or creates owned values in local variables when cache misses occur. This eliminates unnecessary memory allocations and copies during the training forward pass, achieving approximately 7.4% performance improvement (from ~31.46ms to ~29.13ms). A new benchmark is included to measure the optimization impact.

⏱️ Estimated Review Time: 5-15 minutes

💡 Review Order Suggestion

Order	File Path
1	Cargo.toml
2	benches/richards_glu_bench.rs
3	src/richards/richards_glu.rs

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[recurseml]

Review by RecurseML

🔍 Review performed on 2f07c31..34ffc48

✨ No bugs found, your code is sparkling clean

✅ Files analyzed, no issues (3)

• Cargo.toml
• benches/richards_glu_bench.rs
• src/richards/richards_glu.rs