Fix ProveSlow tiny-iteration crash on macOS ARM (there was a regression in my regression)

[hoffmang9]

Summary

• Fixes the macOS ARM optimized regression failure in ProverSlowRegressionTest by guarding tiny-iteration parameter estimation in ApproximateParameters.
• For very small iteration counts, avoids undefined log(log(x)) behavior by clamping to a minimal valid k=1 path.
• This follows the earlier Linux regression-linking fix already in main; there was a regression in my regression.

Test plan

• Build regression_unit_tests locally
• Run ./build-regression/regression_unit_tests --gtest_filter='ProverSlowRegressionTest.*'
• Confirm both tiny-iteration tests pass

Made with Cursor

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Note

Low Risk
Small, localized change that only affects parameter estimation for tiny iteration counts; main proving logic is unchanged.

Overview
Prevents ProveSlow from crashing on very small num_iterations by guarding ApproximateParameters in src/prover_slow.h against invalid log(log(x)) input.

When the intermediate value is <= 1, the function now returns early with a minimal valid setting (k = 1), avoiding undefined math during parameter estimation while leaving the normal estimation path unchanged for typical iteration counts.

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