⚡ Bolt: Optimize auto_k_selection distance calculations with early exits

[teerthsharma]

💡 What:
In aether-core::ml::clustering::auto_k_selection, the distance() function which invokes libm::sqrt was called repeatedly in an $O(N^2)$ neighborhood scan. The optimization pre-calculates the squared epsilon (eps_sq) threshold, asserting its validity once before entering the loop. The sqrt is eliminated completely by checking !(sum < eps_sq) within an inline distance accumulation loop.

🎯 Why:
Inside high-frequency geometric neighborhood scans, calling sqrt creates significant computational overhead that is fundamentally unnecessary when simple threshold checking is needed.

📊 Impact:
Removes $O(N^2)$ calls to sqrt in the Betti 0 component counting phase, significantly speeding up auto-k discovery.

🔬 Measurement:
Running cargo test -p aether-core clustering maintains the correct output while bypassing redundant floating-point operations.

Additionally updated the auto_k_selection increment bug to maintain functionality and verified with passing test suites.

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PR created automatically by Jules for task 8221590513658495514 started by @teerthsharma

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