fix(ci): ensure release notes end with newline before heredoc delimiter

cliff.toml has trim=true which strips git-cliff's trailing newline.
When written to GITHUB_OUTPUT via heredoc, the closing delimiter was
appended to the last content line instead of its own line, causing
"Matching delimiter not found" error.

Added printf '\n' in the workflow and echo "" in generate-notes to
guarantee a newline before the heredoc closing delimiter.

Impact: Release workflow no longer fails when generating release notes.

.github/workflows/release.yml

@@ -249,6 +249,7 @@ jobs:
           {
             echo "notes<<${NOTES_DELIM}"
             cat release-notes.md
+            printf '\n'  # Ensure content ends with newline (git-cliff trim=true removes it)
             echo "${NOTES_DELIM}"
           } >> $GITHUB_OUTPUT
 

scripts/release/generate-notes

@@ -344,6 +344,7 @@ EOF
     fi
 
     git-cliff --config "$CLIFF_CONFIG" "${FROM_TAG}..${TO_TAG}"
+    echo ""  # Ensure output ends with newline (cliff.toml trim=true removes trailing newline)
 
     if [ "$CLIFF_CONFIG" = "/tmp/cliff.toml" ]; then
         rm -f /tmp/cliff.toml