fix: update workflow configurations

- Fix beta tag passing in release-staging.yml to use RELEASE_TAG env var
- Add staging branch to pr-check.yml trigger branches

Author: Seungwoo321

.github/workflows/pr-check.yml

@@ -5,6 +5,7 @@ on:
     branches:
       - main
       - develop
+      - staging
 
 jobs:
   lint-and-type-check:

.github/workflows/release-staging.yml

@@ -121,7 +121,7 @@ jobs:
         id: publish
         run: |
           # Publish with beta tag
-          node scripts/release-packages.cjs beta
+          RELEASE_TAG=beta node scripts/release-packages.cjs
           
           # Collect published versions
           echo "published_versions<<EOF" >> $GITHUB_OUTPUT