test: add validation functions for autonomous pipeline testing

Created test files to verify full pipeline flow:
- add.ts - Basic math functions (add, subtract, multiply, divide)
- add.test.ts - Comprehensive test suite with Bun test framework

These files will be used to test:
- @sdet-engineer: Test writing (TDD)
- @lead-developer: Implementation
- @code-skeptic: Code review
- @security-auditor: Security check
- E2E pipeline flow

src/validation/add.test.ts

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+// Test file for validation functions
+import { describe, it, expect } from 'bun:test'
+import { add, subtract, multiply, divide } from './add'
+
+describe('Validation Functions', () => {
+  describe('add', () => {
+    it('should add two positive numbers', () => {
+      expect(add(2, 3)).toBe(5)
+    })
+    
+    it('should add negative numbers', () => {
+      expect(add(-1, -2)).toBe(-3)
+    })
+    
+    it('should add zero', () => {
+      expect(add(5, 0)).toBe(5)
+    })
+    
+    it('should handle floating point', () => {
+      expect(add(0.1, 0.2)).toBeCloseTo(0.3)
+    })
+  })
+  
+  describe('subtract', () => {
+    it('should subtract two numbers', () => {
+      expect(subtract(5, 3)).toBe(2)
+    })
+    
+    it('should handle negative result', () => {
+      expect(subtract(3, 5)).toBe(-2)
+    })
+  })
+  
+  describe('multiply', () => {
+    it('should multiply two numbers', () => {
+      expect(multiply(4, 3)).toBe(12)
+    })
+    
+    it('should multiply by zero', () => {
+      expect(multiply(5, 0)).toBe(0)
+    })
+  })
+  
+  describe('divide', () => {
+    it('should divide two numbers', () => {
+      expect(divide(10, 2)).toBe(5)
+    })
+    
+    it('should throw on division by zero', () => {
+      expect(() => divide(5, 0)).toThrow('Division by zero')
+    })
+  })
+})

src/validation/add.ts

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+// Test file for autonomous pipeline testing
+// This should pass through: requirement-refiner → sdet-engineer → lead-developer → code-skeptic
+
+/**
+ * Adds two numbers
+ * @param a - First number
+ * @param b - Second number
+ * @returns Sum of a and b
+ */
+export function add(a: number, b: number): number {
+  return a + b
+}
+
+/**
+ * Subtracts second number from first
+ * @param a - First number
+ * @param b - Second number
+ * @returns Difference of a and b
+ */
+export function subtract(a: number, b: number): number {
+  return a - b
+}
+
+/**
+ * Multiplies two numbers
+ * @param a - First number
+ * @param b - Second number
+ * @returns Product of a and b
+ */
+export function multiply(a: number, b: number): number {
+  return a * b
+}
+
+/**
+ * Divides first number by second
+ * @param a - Dividend
+ * @param b - Divisor
+ * @returns Quotient of a and b
+ * @throws Error if b is zero
+ */
+export function divide(a: number, b: number): number {
+  if (b === 0) {
+    throw new Error('Division by zero')
+  }
+  return a / b
+}