Trigger docker build on branch name rather than PR label

gh pr create --label fails consistently due to token permission
constraints. The sync branch name (sync/upstream-v*) is a more
reliable signal than a label and requires no extra API calls.
Remove label logic from the sync workflow entirely.

Author: trevorgowing

.github/workflows/teal-docker-publish.yml

@@ -3,7 +3,7 @@ name: Build and Publish Docker Image
 # Triggers:
 #   1. Push to master whose commit message starts with "chore: sync upstream v..."
 #      (i.e. a clean auto-merge from teal-sync-upstream-release.yml)
-#   2. A pull_request with the "upstream-sync" label is merged to master
+#   2. A pull_request from a sync/upstream-v* branch is merged to master
 #      (i.e. a conflict resolution PR from teal-sync-upstream-release.yml)
 #   3. Manual dispatch — useful for rebuilding any version on demand.
 
@@ -59,10 +59,9 @@ jobs:
 
           elif [[ "$EVENT" == "pull_request" ]]; then
             MERGED="${{ github.event.pull_request.merged }}"
-            LABELS='${{ toJson(github.event.pull_request.labels.*.name) }}'
             BRANCH="${{ github.event.pull_request.head.ref }}"
 
-            if [[ "$MERGED" == "true" ]] && echo "$LABELS" | grep -q '"upstream-sync"'; then
+            if [[ "$MERGED" == "true" ]] && [[ "$BRANCH" =~ ^sync/upstream-v ]]; then
               VERSION=$(echo "$BRANCH" | grep -oP 'v[0-9]+\.[0-9x.]+' || true)
               if [[ -z "$VERSION" ]]; then
                 VERSION=$(gh api repos/metabase/metabase/releases/latest --jq '.tag_name')

.github/workflows/teal-sync-upstream-release.yml

@@ -142,17 +142,11 @@ jobs:
           echo "> \`frontend/src/metabase/ui/colors/constants/themes/dark.ts\`" >> "$BODY_FILE"
           echo "> \`src/metabase/appearance/settings.clj\`" >> "$BODY_FILE"
 
-          gh label create "upstream-sync" \
-            --color "0075ca" \
-            --description "Automatic upstream release sync" \
-            --repo "$GITHUB_REPOSITORY" 2>/dev/null || true
-
           gh pr create \
             --title "chore: sync upstream $TAG (merge conflicts)" \
             --body-file "$BODY_FILE" \
             --base master \
-            --head "$BRANCH" \
-            --label "upstream-sync"
+            --head "$BRANCH"
 
       - name: Summary
         if: always()