Move onto the 0.4.x line

A stream now says it cannot be seeked instead of answering false, a response and a request
always have a header bag and a body, an environment variable which was never set gives back
the default rather than a TypeError, and the kernel no longer asks for a dispatcher, so the
stack takes a coordinated step together and asks for `^0.4` of its own packages.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ARqBYLxrHqevcVmxHkpJcZ

Author: Radoslaw Ziemniewicz

composer.json

@@ -27,11 +27,11 @@
     },
     "require-dev": {
         "phpstan/phpstan": "^2.0",
-        "quillstack/unit-tests": "^0.6"
+        "quillstack/unit-tests": "^0.7"
     },
     "extra": {
         "branch-alias": {
-            "dev-main": "0.3.x-dev"
+            "dev-main": "0.4.x-dev"
         }
     },
     "scripts": {