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>

tests/Unit/Module/SearchProviderCollectionTest.php

@@ -20,7 +20,7 @@ final class SearchProviderCollectionTest extends TestCase
         if (!($GLOBALS['minty_app_container'] ?? null) instanceof \MintyPHP\App\AppContainer
             || !($GLOBALS['minty_app_container'])->has(ModuleRegistry::class)) {
             // Restore the bootstrap container that has the module registry
-            $container = require dirname(__DIR__, 3) . '/lib/App/registerContainer.php';
+            $container = require dirname(__DIR__, 3) . '/core/App/registerContainer.php';
             $this->pushAppContainer($container);
             setAppContainer($container);
         }