ci: harden pnpm sticky cache on PRs

.github/actions/setup-pnpm-store-cache/action.yml

@@ -10,7 +10,7 @@ inputs:
     required: false
     default: "node24"
   use-sticky-disk:
-    description: Use Blacksmith sticky disks instead of actions/cache for pnpm store.
+    description: Use Blacksmith sticky disks instead of actions/cache for pnpm store on trusted runs.
     required: false
     default: "false"
   use-restore-keys:
@@ -51,10 +51,10 @@ runs:
       run: echo "path=$(pnpm store path --silent)" >> "$GITHUB_OUTPUT"
 
     - name: Mount pnpm store sticky disk
-      if: inputs.use-sticky-disk == 'true'
+      if: inputs.use-sticky-disk == 'true' && github.event_name != 'pull_request'
       uses: useblacksmith/stickydisk@v1
       with:
-        key: ${{ github.repository }}-pnpm-store-${{ runner.os }}-${{ inputs.cache-key-suffix }}
+        key: ${{ github.repository }}-pnpm-store-${{ runner.os }}-${{ github.ref_name }}-${{ inputs.cache-key-suffix }}-${{ hashFiles('pnpm-lock.yaml') }}
         path: ${{ steps.pnpm-store.outputs.path }}
 
     - name: Restore pnpm store cache (exact key only)