ci: always pnpm install (workspace symlinks don't survive node_modules cache)

Author: GSTJ

.github/workflows/branch-validation.yml

@@ -39,18 +39,8 @@ jobs:
         with:
           node-version: 20.x
 
-      - name: "📦 Cache Node Modules"
-        uses: actions/cache@v4.2.3
-        id: cache-node-modules
-        with:
-          path: node_modules
-          key: ${{ runner.os }}-node-modules-${{ hashFiles('**/pnpm-lock.yaml') }}
-          restore-keys: |
-            ${{ runner.os }}-node-modules-
-
       - name: 📦 Install Dependencies
-        if: steps.cache-node-modules.outputs.cache-hit != 'true'
-        run: pnpm install
+        run: pnpm install --frozen-lockfile
 
       - name: 👨‍⚕️ Expo Doctor
         run: pnpm run doctor