ci: make playground-wasm lock push branch-aware

git push origin main was hardcoded, so a workflow_dispatch off a feature
branch would fail at the final step (no local main ref). Push back to
GITHUB_REF_NAME instead: identical on main, and pre-merge test runs bump
the lock on their own branch.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: lightsofapollo

.github/workflows/playground-wasm.yml

@@ -61,6 +61,8 @@ jobs:
           echo "$tag" > website/playground-wasm.lock
 
       - name: Commit lock bump
+        # Pushes back to the ref the workflow ran on: main for the normal
+        # push-triggered flow, the dispatched branch for pre-merge test runs.
         run: |
           set -euo pipefail
           if git diff --quiet -- website/playground-wasm.lock; then
@@ -71,5 +73,5 @@ jobs:
           git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
           git add website/playground-wasm.lock
           git commit -m "chore: bump playground wasm to $(cat website/playground-wasm.lock) [skip ci]"
-          git pull --rebase origin main
-          git push origin main
+          git pull --rebase origin "$GITHUB_REF_NAME"
+          git push origin "HEAD:$GITHUB_REF_NAME"