chore: bump lib-core.panel dep to 0.4.0

Engine resolver does exact strcmp on dep versions, so consumer manifests
must pin the new lib-core.panel 0.4.0 to keep load-time resolution green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

manifest.module

@@ -14,7 +14,7 @@
         {"id":"lib-core.composition","version":"0.3.0"},
         {"id":"lib-core.camera","version":"0.3.0"},
         {"id":"lib-core.input","version":"0.4.0"},
-        {"id":"lib-core.panel","version":"0.3.0"},
+        {"id":"lib-core.panel","version":"0.4.0"},
         {"id":"lib-asset.prototype-blob-geom","version":"0.1.0"}
     ]
 }