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/Architecture/AuditModuleIsolationContractTest.php

@@ -8,7 +8,7 @@ final class AuditModuleIsolationContractTest extends TestCase
 {
     public function testCoreServiceAuditDirectoryContainsOnlyInterfaces(): void
     {
-        $dir = dirname(__DIR__, 2) . '/lib/Service/Audit';
+        $dir = dirname(__DIR__, 2) . '/core/Service/Audit';
         self::assertDirectoryExists($dir);
 
         $files = array_values(array_filter(
@@ -37,7 +37,7 @@ final class AuditModuleIsolationContractTest extends TestCase
         self::assertSame(
             $allowed,
             $files,
-            'lib/Service/Audit/ should contain only interfaces and null implementations, found: ' . implode(', ', $files)
+            'core/Service/Audit/ should contain only interfaces and null implementations, found: ' . implode(', ', $files)
         );
     }
 
@@ -45,14 +45,14 @@ final class AuditModuleIsolationContractTest extends TestCase
     {
         $root = dirname(__DIR__, 2);
         self::assertDirectoryDoesNotExist(
-            $root . '/lib/Repository/Audit',
-            'Audit repository classes should live in modules/audit/lib, not in Core lib/Repository/Audit'
+            $root . '/core/Repository/Audit',
+            'Audit repository classes should live in modules/audit/lib, not in Core core/Repository/Audit'
         );
     }
 
     public function testCoreDomainTaxonomyHasNoAuditEnums(): void
     {
-        $dir = dirname(__DIR__, 2) . '/lib/Domain/Taxonomy';
+        $dir = dirname(__DIR__, 2) . '/core/Domain/Taxonomy';
         if (!is_dir($dir)) {
             self::addToAssertionCount(1);
             return;
@@ -90,7 +90,7 @@ final class AuditModuleIsolationContractTest extends TestCase
     {
         $root = dirname(__DIR__, 2);
         self::assertFileDoesNotExist(
-            $root . '/lib/Http/ApiSystemAuditReporter.php',
+            $root . '/core/Http/ApiSystemAuditReporter.php',
             'ApiSystemAuditReporter should live in modules/audit/lib, not in Core lib/Http'
         );
     }
@@ -114,7 +114,7 @@ final class AuditModuleIsolationContractTest extends TestCase
     {
         $root = dirname(__DIR__, 2);
         self::assertFileDoesNotExist(
-            $root . '/lib/Service/Scheduler/Handler/SystemAuditPurgeJobHandler.php',
+            $root . '/core/Service/Scheduler/Handler/SystemAuditPurgeJobHandler.php',
             'SystemAuditPurgeJobHandler should live in modules/audit, not in Core'
         );
     }