ci(sync): make tag mirror push best-effort

Upstream has 6000+ tags. A single collision with a protected tag name
(or a transient GitHub API hiccup partway through the push) would
otherwise fail the entire sync run, stopping gix-main freshness. Tags
are nice-to-have for our mirror, not load-bearing — gix-main's HEAD
pointing at upstream/main is what actually matters.

Log a warning if the tag push exits non-zero so we have a trail, but
don't fail the job.

Co-authored-by: Claude <claude@anthropic.com>

Author: Mbd06b

.github/workflows/sync-upstream.yml

@@ -62,6 +62,17 @@ jobs:
         if: steps.ff.outputs.changed == 'true'
         run: git push origin gix-main
 
-      - name: Push mirrored tags
+      # Tags are nice-to-have but not critical for our sync purposes.
+      # Upstream has 6000+ tags; a single collision or protected-tag rule
+      # would otherwise kill the whole run. Best-effort push, report in logs.
+      - name: Push mirrored tags (best effort)
         if: steps.ff.outputs.changed == 'true'
-        run: git push origin --tags
+        continue-on-error: true
+        run: |
+          set +e
+          git push origin --tags 2>&1 | tee push-tags.log
+          status=${PIPESTATUS[0]}
+          if [ "$status" -ne 0 ]; then
+            echo "::warning::Tag mirror push exited with status $status; some tags may not have synced. See push-tags.log above."
+          fi
+          exit 0