Optimize VectorQuantizeTask min/max finding with single-pass algorithm

[Copilot]

The quantizeToUint8 and quantizeToUint16 methods used spread operators with Math.min(...values) and Math.max(...values), causing performance degradation and potential stack overflow on large vectors.

Changes:

• Added findMinMax() helper that computes min/max in single pass using explicit loop
• Updated quantizeToUint8 and quantizeToUint16 to use optimized helper
• Fixed edge case: empty arrays now return { min: 0, max: 1 } to prevent division by zero

Before:

const min = Math.min(...values);  // Two iterations + intermediate arrays
const max = Math.max(...values);

After:

const { min, max } = this.findMinMax(values);  // Single pass, no spreading

Addresses feedback: #154 (comment)

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