chore(validation): enforce package graph boundaries

Reject internal package version drift, dependency cycles, and runtime-to-integration reverse dependencies before launching the external UPM consumer validation.

Tools/UpmConsumerValidation/README.md

@@ -1,14 +1,17 @@
 # UPM Consumer Validation
 
 `Validate-UpmConsumer.ps1` verifies the package graph from outside the main Unity
-project. It performs three checks:
+project. It performs five checks:
 
 1. Every dependency on another local `com.cneicy.*` package must use that
    package's current `package.json` version.
-2. A temporary Unity project is created under `Temp/UpmConsumerValidation`, all
+2. The local package graph must be acyclic.
+3. A normal package must not depend on a `*-integration-*` package. Integration
+   packages may depend on each other, and starter packages may aggregate them.
+4. A temporary Unity project is created under `Temp/UpmConsumerValidation`, all
    local packages are installed through `file:` UPM dependencies, package tests
    are enabled, and Unity must load every package and asmdef.
-3. The same temporary UPM consumer project runs all package EditMode tests.
+5. The same temporary UPM consumer project runs all package EditMode tests.
 
 Run with the Unity version declared by this repository:
 
@@ -16,6 +19,12 @@ Run with the Unity version declared by this repository:
 ./Tools/UpmConsumerValidation/Validate-UpmConsumer.ps1
 ```
 
+Run only the package graph checks without starting Unity:
+
+```powershell
+./Tools/UpmConsumerValidation/Validate-UpmConsumer.ps1 -GraphOnly
+```
+
 Use `-UnityEditorPath` when the matching editor is not installed in a standard
 location. Pass `-KeepProject` to retain the temporary project, reports, and Unity logs for
 investigation. `-SkipTests` is only for a quick package-resolution diagnostic and is not the