Hoist QA toolchain to the monorepo

One pinned toolchain (pint, phpstan, rector) in the root composer.json,
one canonical pint.json for every package, run via bin/monorepo check
(--fix to apply) in CI alongside tests. phpstan.neon and rector.php
stay per-package as they encode per-library decisions.

Applies the canonical style to cli, platform and queue, the Stringable
interface rector wants on client's PSR-7 classes, and drops the
now-pointless nullsafe operators phpstan flags in http's RouterTest.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: loks0n

pint.json

@@ -80,8 +80,8 @@ public function testCanMatchHttpMethod(): void
         $this->assertSame($routeGET, Router::match(Http::REQUEST_METHOD_GET, '/')?->route);
         $this->assertSame($routePOST, Router::match(Http::REQUEST_METHOD_POST, '/')?->route);
 
-        $this->assertNotSame($routeGET, Router::match(Http::REQUEST_METHOD_POST, '/')?->route);
-        $this->assertNotSame($routePOST, Router::match(Http::REQUEST_METHOD_GET, '/')?->route);
+        $this->assertNotSame($routeGET, Router::match(Http::REQUEST_METHOD_POST, '/')->route);
+        $this->assertNotSame($routePOST, Router::match(Http::REQUEST_METHOD_GET, '/')->route);
     }
 
     public function testCanMatchAlias(): void