fix(fp8_cast): Add robust memory management and error handling

[ajwise9]

• Add try-catch block for memory management operations
• Implement graceful error handling for memory allocation failures
• Add explicit CUDA memory cleanup
• Protect against potential race conditions in file loading

This change improves stability when converting large models by:

• Preventing crashes from out-of-memory conditions
• Ensuring proper cleanup of GPU resources
• Adding error reporting for debugging

[ajwise9]

fix(fp8_cast): Add robust memory management and error handling

[mowentian]

no fallback strategy for oom error, so just raise err and failed is simple and fine