Add test coverage for VectorUtils module

[Copilot]

Addresses code review feedback requesting test coverage for the VectorUtils module (magnitude, inner, normalize, normalizeNumberArray).

Test Coverage Added

52 test cases covering:

• magnitude() - L2 norm calculation across Float16/32/64Array, Int8/16Array, Uint8/16Array, number arrays; zero vectors, negative values, large vectors
• inner() - Dot product for all typed array types; orthogonal vectors, zero vectors
• normalize() - Unit length normalization with type preservation; Float16Array → Float32Array conversion; zero vector handling via throwOnZero parameter
• normalizeNumberArray() - Number array normalization; immutability verification; zero vector handling

Edge cases tested: zero vectors, single elements, negative/mixed values, already normalized inputs, large vectors (1000 elements).

// Example test structure
test("should normalize Float32Array to unit length", () => {
  const vector = new Float32Array([3, 4]);
  const result = normalize(vector);
  expect(result).toBeInstanceOf(Float32Array);
  expect(magnitude(result)).toBeCloseTo(1, 5);
});

test("should throw error for zero vector by default", () => {
  const vector = new Float32Array([0, 0, 0]);
  expect(() => normalize(vector)).toThrow("Cannot normalize a zero vector.");
});

Tests follow repository's vitest patterns. CI will validate execution.

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