fix: restrict release workflow to release/* branches only

Add branch check to ensure release workflow only runs for PRs
from release/* branches. This prevents unintended releases from
other branches merged to master.

Author: azu

.github/workflows/release.yml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ubuntu-latest
     outputs:
       EXISTS_TAG: ${{ steps.tag_check.outputs.EXISTS_TAG }}
-    if: github.event.pull_request.merged == true
+    if: github.event.pull_request.merged == true && startsWith(github.head_ref, 'release/')
     steps:
       - name: Checkout
         uses: actions/checkout@08eba0b27e820071cde6df949e0beb9ba4906955 # v4.3.0