feat: add ConfigValidator for plugin JSON schema validation

Validates project config against plugin getConfigSchema() definitions.
Supports: type checking, required fields, enum values, nested objects,
arrays, string minLength/pattern, number min/max, unknown property warnings.

7 unit tests covering all validation paths.

Closes #105

Authored-by: Moko Consulting
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/Unit/ConfigValidatorTest.php

@@ -0,0 +1,141 @@
+<?php
+
+/* Copyright (C) 2026 Moko Consulting <hello@mokoconsulting.tech>
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+declare(strict_types=1);
+
+namespace MokoStandards\Tests\Unit;
+
+use MokoEnterprise\ConfigValidator;
+use PHPUnit\Framework\TestCase;
+
+class ConfigValidatorTest extends TestCase
+{
+    private ConfigValidator $validator;
+
+    protected function setUp(): void
+    {
+        $this->validator = new ConfigValidator();
+    }
+
+    public function testValidConfigPasses(): void
+    {
+        $schema = [
+            'type' => 'object',
+            'properties' => [
+                'name' => ['type' => 'string'],
+                'version' => ['type' => 'string'],
+            ],
+            'required' => ['name'],
+        ];
+
+        $config = ['name' => 'MyProject', 'version' => '1.0'];
+
+        $this->assertTrue($this->validator->validate($config, $schema));
+        $this->assertEmpty($this->validator->getErrors());
+    }
+
+    public function testMissingRequiredField(): void
+    {
+        $schema = [
+            'type' => 'object',
+            'properties' => [
+                'name' => ['type' => 'string'],
+            ],
+            'required' => ['name'],
+        ];
+
+        $this->assertFalse($this->validator->validate([], $schema));
+        $this->assertStringContainsString(
+            'required',
+            $this->validator->getErrors()[0]
+        );
+    }
+
+    public function testEnumValidation(): void
+    {
+        $schema = [
+            'type' => 'object',
+            'properties' => [
+                'type' => [
+                    'type' => 'string',
+                    'enum' => ['component', 'module', 'plugin'],
+                ],
+            ],
+        ];
+
+        $valid = ['type' => 'component'];
+        $this->assertTrue($this->validator->validate($valid, $schema));
+
+        $invalid = ['type' => 'banana'];
+        $this->assertFalse($this->validator->validate($invalid, $schema));
+    }
+
+    public function testNestedObjectValidation(): void
+    {
+        $schema = [
+            'type' => 'object',
+            'properties' => [
+                'db' => [
+                    'type' => 'object',
+                    'properties' => [
+                        'host' => ['type' => 'string'],
+                        'port' => ['type' => 'integer'],
+                    ],
+                    'required' => ['host'],
+                ],
+            ],
+        ];
+
+        $valid = ['db' => ['host' => 'localhost', 'port' => 3306]];
+        $this->assertTrue($this->validator->validate($valid, $schema));
+
+        $invalid = ['db' => ['port' => 3306]];
+        $this->assertFalse($this->validator->validate($invalid, $schema));
+    }
+
+    public function testUnknownPropertiesWarn(): void
+    {
+        $schema = [
+            'type' => 'object',
+            'properties' => [
+                'name' => ['type' => 'string'],
+            ],
+        ];
+
+        $config = ['name' => 'ok', 'extra' => 'unknown'];
+        $this->assertTrue($this->validator->validate($config, $schema));
+        $this->assertNotEmpty($this->validator->getWarnings());
+    }
+
+    public function testTypeMismatch(): void
+    {
+        $schema = [
+            'type' => 'object',
+            'properties' => [
+                'count' => ['type' => 'integer'],
+            ],
+        ];
+
+        $invalid = ['count' => 'not-a-number'];
+        $this->assertFalse($this->validator->validate($invalid, $schema));
+    }
+
+    public function testStringMinLength(): void
+    {
+        $schema = [
+            'type' => 'object',
+            'properties' => [
+                'name' => ['type' => 'string', 'minLength' => 3],
+            ],
+        ];
+
+        $short = ['name' => 'ab'];
+        $this->assertFalse($this->validator->validate($short, $schema));
+
+        $ok = ['name' => 'abc'];
+        $this->assertTrue($this->validator->validate($ok, $schema));
+    }
+}