Add CI drift guard for the CultNet contracts consolidation

REC-032 commit 2: fail cultnet-interop.yml before it installs Node
dependencies if either negative check from commit 1 finds anything:
a *.schema.json file living outside contracts/cultnet/, or a lingering
reference to the retired https://github.com/GameCult/cultnet-ts/contracts
(or .../integration/contracts) namespace anywhere but .voidbot/birth
snapshots. The old-namespace grep uses git grep -I so the deferred
Unity plugin DLL (D4, not rebuilt in this pass) doesn't trip a
permanent false failure.

Verified locally: staging a stray contracts/stray.schema.json and a
stray-id.ts referencing the old namespace makes the guard's logic
report failure for both; removing them makes it pass again against the
real tree.

REC-032.

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

.github/workflows/cultnet-interop.yml

@@ -65,6 +65,29 @@ jobs:
           "KOTLIN_JAVA_HOME=$env:JAVA_HOME" | Out-File -FilePath $env:GITHUB_ENV -Append
           "$kotlinHome\bin" | Out-File -FilePath $env:GITHUB_PATH -Append
 
+      - name: Verify CultNet schema contracts stayed consolidated
+        shell: pwsh
+        run: |
+          $ErrorActionPreference = "Stop"
+          $stray = git ls-files '*.schema.json' | Where-Object { $_ -notmatch '^contracts/cultnet/' }
+          # -I skips binary files: unity/org.gamecult.cultlib/Runtime/Plugins/GameCult.Networking.dll
+          # still embeds the retired namespace until it is rebuilt (REC-032 D4, deferred).
+          $oldNamespace = git grep -I -lE 'GameCult/cultnet-ts/(integration/)?contracts' -- ':!.voidbot'
+          if ($LASTEXITCODE -eq 2) {
+            throw "git grep failed"
+          }
+          if ($stray) {
+            Write-Host "Schema files found outside contracts/cultnet/:"
+            $stray | ForEach-Object { Write-Host "  $_" }
+          }
+          if ($oldNamespace) {
+            Write-Host "Files still referencing the retired GameCult/cultnet-ts contracts namespace:"
+            $oldNamespace | ForEach-Object { Write-Host "  $_" }
+          }
+          if ($stray -or $oldNamespace) {
+            throw "CultNet schema contracts drifted out of contracts/cultnet/ (REC-032). See CultLib/contracts/cultnet/ and rewrite any `$id back to https://github.com/GameCult/CultLib/contracts/cultnet/."
+          }
+
       - name: Install Node dependencies
         run: npm install --no-package-lock