docs(spec): add kcode DevKit quality gate to SPEC-001

Add 'Quality Gate (kcode DevKit)' section:
- kcode command reference table (quality, test, analyse, cs:fix, security)
- Direct tool access via .kcode/vendor/bin/ (phpstan, psalm --alter,
  php-cs-fixer --dry-run, phpunit --filter)
References ARFA Spec V4.0 §16 (DevKit Infrastructure Standard).

Author: walmir-silva

docs/spec/SPEC-001-serializer-engine.md

@@ -62,3 +62,48 @@ Reads `#[Serialize]` attributes:
 $result = $serializer->serialize($dto, 'json', ['public']);
 $object = $serializer->deserialize($json, UserDto::class, 'json');
 ```
+
+## Quality Gate (kcode DevKit)
+
+This component uses `kcode` (KaririCode DevKit global binary) for all quality checks.
+See [ARFA Spec V4.0 §16](https://github.com/KaririCode-Framework/kariricode-devkit) for the full infrastructure standard.
+
+### Bootstrap (once per machine/CI)
+
+```bash
+# Install kcode globally
+curl -L https://github.com/KaririCode-Framework/kariricode-devkit/releases/latest/download/kcode.phar \
+     -o /usr/local/bin/kcode && chmod +x /usr/local/bin/kcode
+
+# Bootstrap project toolchain
+kcode init
+```
+
+### Common Commands
+
+| Command | Description |
+|---------|-------------|
+| `kcode quality` | Full pipeline: cs-fix → analyse → test |
+| `kcode test` | PHPUnit + pcov coverage |
+| `kcode analyse` | PHPStan L9 + Psalm L1 |
+| `kcode cs:fix` | Apply KaririCode code style |
+| `kcode cs:fix --check` | Dry-run style check |
+| `kcode security` | `composer audit` vulnerability scan |
+
+### Internal Tool Direct Access
+
+After `kcode init`, tools are under `.kcode/vendor/bin/`:
+
+```bash
+# PHPStan with custom flags
+.kcode/vendor/bin/phpstan analyse --level=9 --configuration=.kcode/phpstan.neon src/
+
+# Psalm — auto-add #[Override]
+.kcode/vendor/bin/psalm --config=.kcode/psalm.xml --alter --issues=MissingOverrideAttribute
+
+# php-cs-fixer — preview diff
+.kcode/vendor/bin/php-cs-fixer fix --config=.kcode/php-cs-fixer.php --dry-run --diff
+
+# PHPUnit — single test filter
+.kcode/vendor/bin/phpunit --configuration=.kcode/phpunit.xml.dist --filter=testMyMethod
+```