refactor: rename lib/ to core/ for clearer core-module separation

Rename the top-level lib/ directory to core/ so the project root
immediately communicates which code is core platform and which lives
in modules/. PHP namespaces (MintyPHP\*) are unchanged — only the
Composer PSR-4 path mapping moves from lib/ to core/.

Module-internal lib/ directories (modules/*/lib/) are untouched.

Updated across the full stack:
- composer.json PSR-4 mapping
- bootstrap entry points (web/index.php, bin/*, tests/bootstrap.php)
- tooling configs (phpstan.neon, phpunit.xml, php-cs-fixer)
- 26 architecture contract tests
- enforcement-policy, guard-catalog, quality-gates
- all documentation (CLAUDE.md, README, 25 docs/, .agents/skills/)
- bin/qa-extended.sh search paths
- .claude/settings.local.json permission paths

Workflow: .agents/runs/CORE-LIB-RENAME-001/ (Analyst → Planner →
Executor → Code Review (4 findings fixed) → Security Review →
Acceptance Test → Finalizer)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/App/Module/ModuleI18nLoader.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace MintyPHP\App\Module;
+
+use MintyPHP\I18n;
+use ReflectionProperty;
+
+/**
+ * Preloads core + module translations into I18n::$strings at boot time.
+ *
+ * Since I18n::$strings is private static and lives in a vendor class,
+ * Reflection is used once per locale to inject the merged translation map.
+ */
+final class ModuleI18nLoader
+{
+    /**
+     * @param list<ModuleManifest> $manifests Active module manifests (already sorted)
+     * @param string $coreI18nDir Absolute path to the core i18n/ directory
+     */
+    public static function preload(array $manifests, string $coreI18nDir): void
+    {
+        $locales = ['de', 'en'];
+        $domain = I18n::$domain ?: 'default';
+
+        $prop = new ReflectionProperty(I18n::class, 'strings');
+
+        foreach ($locales as $locale) {
+            // Load core file
+            $coreFile = $coreI18nDir . '/' . $domain . '_' . $locale . '.json';
+            $merged = is_file($coreFile)
+                ? (json_decode(file_get_contents($coreFile), true) ?: [])
+                : [];
+
+            // Merge each module's translations on top
+            foreach ($manifests as $manifest) {
+                if ($manifest->i18nPath === null) {
+                    continue;
+                }
+                $moduleFile = $manifest->i18nPath . '/' . $domain . '_' . $locale . '.json';
+                if (!is_file($moduleFile)) {
+                    continue;
+                }
+                $moduleStrings = json_decode(file_get_contents($moduleFile), true);
+                if (is_array($moduleStrings)) {
+                    $merged = array_merge($merged, $moduleStrings);
+                }
+            }
+
+            // Inject via Reflection into I18n::$strings
+            $strings = $prop->getValue();
+            $strings[$domain][$locale] = $merged;
+            $prop->setValue(null, $strings);
+        }
+    }
+}