fix: backstage-workshop CI - proper working directory and Yarn Berry

- Run all build steps in backstage/ subdirectory
- Enable Corepack for Yarn 4.x
- Use --skipLibCheck for tsc
- Remove path filters to ensure CI triggers

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: JoshLuedeman

.github/workflows/ci.yml

@@ -1,15 +1,11 @@
 name: "🎭 Backstage CI"
 
 on:
-  workflow_dispatch:
   push:
     branches: [main]
-    paths:
-      - 'backstage/**'
   pull_request:
     branches: [main]
-    paths:
-      - 'backstage/**'
+  workflow_dispatch:
 
 permissions:
   contents: read
@@ -38,7 +34,7 @@ jobs:
         run: yarn install --immutable
 
       - name: TypeScript Check
-        run: yarn tsc
+        run: yarn tsc --skipLibCheck
 
       - name: Build
         run: yarn build:all
@@ -47,4 +43,6 @@ jobs:
         run: yarn lint:all
 
       - name: Test
-        run: yarn test
+        run: yarn test:all
+        env:
+          CI: true