feat: enhance numeric coerce() to handle empty strings

Enhanced coercion behavior for better form data handling:

## IntValidator & FloatValidator Changes:
- Empty strings ('') now coerce to 0 and 0.0 respectively
- Maintains backward compatibility for existing numeric coercion
- Addresses real-world HTML form scenarios where empty fields are common

## Test Coverage Added:
- 6 new tests across IntValidatorTest.php and FloatValidatorTest.php
- Tests cover empty string coercion, numeric strings, and error cases
- All tests pass (15 tests, 51 assertions)

## Roadmap Updates:
- Removed redundant emptyToZero() method from roadmap
- Added Enhanced coerce() as completed feature
- Updated examples to show cleaner API usage

## Real-World Impact:
Before: Validator::isInt()->coerce()->validate('') // ❌ ValidationException
After:  Validator::isInt()->coerce()->validate('') // ✅ Returns 0

This makes form validation significantly more practical and intuitive.

Author: lemmon

ROADMAP.md

@@ -106,8 +106,7 @@ $formValidator = Validator::isAssociative([
         ->nullifyEmpty()                                // Works across all types ✅
         ->coerce(),
     'salary' => Validator::isFloat()
-        ->emptyToZero()                                 // New numeric-specific method
-        ->coerce(),
+        ->coerce(),                                     // Enhanced: empty strings → 0.0
     'tags' => Validator::isArray()
         ->filterEmpty()                                 // Remove empty values
         ->reindex()                                     // Re-index after filtering
@@ -116,14 +115,14 @@ $formValidator = Validator::isAssociative([
 
 // Compare: Before vs After
 // Before (verbose):
-->transform(fn($v) => $v === '' ? null : $v)
-->transform(fn($v) => array_filter($v))
-->transform(fn($v) => array_values($v))
+->transform(fn($v) => $v === '' ? 0 : $v)               // Empty string to zero
+->transform(fn($v) => array_filter($v))                 // Remove empty values
+->transform(fn($v) => array_values($v))                 // Re-index array
 
 // After (clean and discoverable):
-->nullifyEmpty()                                        // ✅ Already exists!
-->filterEmpty()
-->reindex()
+->coerce()                                              // ✅ Enhanced: empty strings → 0!
+->filterEmpty()                                         // Clean array method
+->reindex()                                             // Clean array method
 
 // Complex array processing with existing tools:
 $arrayValidator = Validator::isArray()
@@ -160,7 +159,7 @@ $stringValidator = Validator::isString()
 ### Numeric Transformations
 - [ ] **`clamp(min, max)`** - Restrict numbers to range (not obvious: max(min, min(max, value)))
 - [ ] **`round(precision)`** - Round with precision parameter (convenience for common pattern)
-- [ ] **`emptyToZero()`** - Convert empty strings to 0 (common in numeric forms)
+- [x] ✅ **Enhanced `coerce()`** - Empty strings → 0 for numeric types (already implemented!)
 - [x] ✅ **`nullifyEmpty()`** - Convert empty strings to null (already implemented!)
 - [ ] **`transform()`** / **`pipe()`** - Generic transformation methods (core functionality)
 

src/Lemmon/FloatValidator.php

@@ -11,6 +11,9 @@ class FloatValidator extends FieldValidator
      */
     protected function coerceValue(mixed $value): mixed
     {
+        if ($value === '') {
+            return 0.0;
+        }
         if (is_numeric($value)) {
             return is_int($value) ? (float) $value : (float) $value;
         }

src/Lemmon/IntValidator.php

@@ -11,6 +11,9 @@ class IntValidator extends FieldValidator
      */
     protected function coerceValue(mixed $value): mixed
     {
+        if ($value === '') {
+            return 0;
+        }
         return is_numeric($value) ? (int) $value : $value;
     }
 

tests/FloatValidatorTest.php

@@ -2,6 +2,27 @@
 
 use Lemmon\Validator;
 
+it('should coerce empty string to zero', function () {
+    $validator = Validator::isFloat()->coerce();
+
+    expect($validator->validate(''))->toBe(0.0);
+});
+
+it('should coerce numeric strings to floats', function () {
+    $validator = Validator::isFloat()->coerce();
+
+    expect($validator->validate('123.45'))->toBe(123.45);
+    expect($validator->validate('0'))->toBe(0.0);
+    expect($validator->validate('-42.7'))->toBe(-42.7);
+    expect($validator->validate('123'))->toBe(123.0);
+});
+
+it('should fail coercion for non-numeric strings', function () {
+    $validator = Validator::isFloat()->coerce();
+
+    $validator->validate('abc');
+})->throws(Lemmon\ValidationException::class, 'Value must be a float');
+
 it('should validate floats', function () {
     $validator = Validator::isFloat();
 

tests/IntValidatorTest.php

@@ -2,6 +2,26 @@
 
 use Lemmon\Validator;
 
+it('should coerce empty string to zero', function () {
+    $validator = Validator::isInt()->coerce();
+
+    expect($validator->validate(''))->toBe(0);
+});
+
+it('should coerce numeric strings to integers', function () {
+    $validator = Validator::isInt()->coerce();
+
+    expect($validator->validate('123'))->toBe(123);
+    expect($validator->validate('0'))->toBe(0);
+    expect($validator->validate('-42'))->toBe(-42);
+});
+
+it('should fail coercion for non-numeric strings', function () {
+    $validator = Validator::isInt()->coerce();
+
+    $validator->validate('abc');
+})->throws(Lemmon\ValidationException::class, 'Value must be an integer');
+
 it('should validate integer ranges', function () {
     $rangeValidator = Validator::isInt()->min(10)->max(100);