Do not fail the screenshot recording job when there is nothing to commit

recordScreenshots.sh runs under `set -e`, and the `git commit -m "Update
screenshots"` at the end of it is unconditional. When a recording run
produces no diff — the common case once the snapshots are already up to
date — `git commit` exits 1 with "nothing to commit, working tree clean"
and takes the whole workflow down with it, reporting a red job for a
successful run.

Stage as before, then return early when the staged diff is empty. `set -e`
is left in place: it was added deliberately so that a failed Gradle run
cannot push a commit that deletes every snapshot. Using `git diff --cached
--quiet` as an `if` condition is `set -e`-safe, because its non-zero "there
are changes" status is consumed by the condition. The early return also
skips the push, which had nothing to send.

.github/workflows/scripts/recordScreenshots.sh

@@ -78,6 +78,10 @@ else
   git config --local user.name "${INPUT_AUTHOR_EMAIL}"
 fi
 git add -A
+if git diff --cached --quiet; then
+  echo "Screenshots are already up to date, nothing to commit."
+  exit 0
+fi
 git commit -m "Update screenshots"
 
 GITHUB_REPO="https://$GITHUB_ACTOR:$TOKEN@github.com/$REPO.git"