fix(bool): skip string coercion for non-scalar values in BoolValidator

- Guard coerceValue with is_scalar before string normalization
- Add tests for array and object inputs with coerce()
- Document scalar-only coercion in API reference
- Record fix in CHANGELOG

Author: lemmon

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+### Fixed
+
+- `BoolValidator::coerce()` no longer string-casts non-scalar values (arrays triggered `E_WARNING`, objects without `__toString` threw `Error`); non-scalars are passed through to type validation, which raises `ValidationException` as for other invalid types
+
 ### Added
 
 - `passthrough()` on `AssociativeValidator` and `ObjectValidator`: copy undeclared keys or public properties from the input to the validated output without validating them; declared schema fields are still validated; values already written from the schema (including `outputKey` targets) are not overwritten by passthrough

docs/api-reference/validator-factory.md

@@ -189,6 +189,8 @@ $result = $coercingValidator->validate('1'); // Returns: true (bool)
 $result = $coercingValidator->validate('false'); // Returns: false (bool)
 ```
 
+With `coerce()`, only **scalar** values are normalized to booleans from common string forms (`true` / `on` / `1`, etc.). Arrays, objects, and other non-scalars are not cast to string; they fail boolean type validation with `ValidationException`.
+
 **Returns:** `BoolValidator` instance with boolean-specific validation methods.
 
 ## Usage Patterns

src/Lemmon/Validator/BoolValidator.php

@@ -16,10 +16,14 @@ protected function coerceValue(mixed $value): mixed
         if ($value === '') {
             return null; // Empty string to null for form safety
         }
-        if (in_array(strtolower((string) $value), ['true', 'on', '1'], true)) {
+        if (!is_scalar($value)) {
+            return $value;
+        }
+        $normalized = strtolower((string) $value);
+        if (in_array($normalized, ['true', 'on', '1'], true)) {
             return true;
         }
-        if (in_array(strtolower((string) $value), ['false', 'off', '0'], true)) {
+        if (in_array($normalized, ['false', 'off', '0'], true)) {
             return false;
         }
         return $value;

tests/BoolValidatorTest.php

@@ -52,3 +52,10 @@
     expect(fn() => $validator->validate('invalid'))->toThrow(ValidationException::class);
     expect(fn() => $validator->validate(123))->toThrow(ValidationException::class);
 });
+
+it('should reject non-scalar values with coercion without PHP warnings or errors', function () {
+    $validator = Validator::isBool()->coerce();
+
+    expect(fn() => $validator->validate([]))->toThrow(ValidationException::class);
+    expect(fn() => $validator->validate(new stdClass()))->toThrow(ValidationException::class);
+});