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>

docs/reference-cli-commands.md

@@ -154,7 +154,7 @@ Voraussetzung fuer den ersten App-Start: `config/config.php` muss vorhanden sein
 
 ## Neue Kommandos anlegen
 
-1. Klasse in `lib/Console/Commands/` erstellen, die `MintyPHP\Console\Command` erweitert.
+1. Klasse in `core/Console/Commands/` erstellen, die `MintyPHP\Console\Command` erweitert.
 2. `name()`, `description()` und `execute()` implementieren.
 3. Optional: `usage()` fuer `--help`-Ausgabe ueberschreiben.