fix: install plugin from tarball when yalc fails

Problem: Yalc link was broken but package.json still referenced it,
causing Strapi to fail loading the plugin.

Solution: When yalc fails, create a tarball of the built plugin and
install it as a real dependency using 'yarn add'. This guarantees
the plugin is in node_modules where Strapi can find it.

Workflow:
- Try yalc (fast if it works)
- If yalc fails → pack plugin + install tarball (reliable)
- Tests can now load the plugin successfully

Author: MSACC

.github/workflows/tests.yml

@@ -45,14 +45,17 @@ jobs:
 
           # Check if yalc succeeded
           if [ ! -d "playground/.yalc/strapi-plugin-config-sync" ]; then
-            echo "Yalc failed, using yarn link as fallback"
-            # Use yarn link instead
-            yarn link
+            echo "Yalc failed, installing from tarball as fallback"
+            # Create tarball and install it
+            yarn pack --filename plugin.tgz
             cd playground
-            yarn link strapi-plugin-config-sync
+            # Remove yalc link from package.json and install from tarball
+            npm pkg delete dependencies.strapi-plugin-config-sync
+            yarn add ../plugin.tgz
+          else
+            cd playground
+            yarn install --unsafe-perm
           fi
-      - name: Install dependencies playground
-        run: cd playground && yarn install --unsafe-perm
       - name: Build playground
         run: yarn playground:build
       # - name: Run unit tests