fix(ci): skip publish when version already exists on npm (#1166)

Multiple CI completions on the same commit trigger duplicate Pipeline
runs. The second run fails with E403 because the version was already
published. Fix by checking npm registry before attempting publish, and
enable cancel-in-progress to avoid redundant runs.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/pipeline.yml

@@ -8,7 +8,7 @@ on:
 
 concurrency:
   group: pipeline-${{ github.sha }}
-  cancel-in-progress: false
+  cancel-in-progress: true
 
 permissions:
   contents: write
@@ -51,7 +51,13 @@ jobs:
           echo "version=$(node -e 'process.stdout.write(require("./package.json").version)')" >> "$GITHUB_OUTPUT"
 
       - name: Publish @dev
-        run: npm publish --tag dev
+        run: |
+          VERSION=$(node -e 'process.stdout.write(require("./package.json").version)')
+          if npm view "gsd-pi@${VERSION}" version 2>/dev/null; then
+            echo "Version ${VERSION} already published — skipping"
+          else
+            npm publish --tag dev
+          fi
         env:
           NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}