Auto-publish npm package when version changes in package.json

Replace tag-based trigger with push-to-main trigger that detects
version changes in napi/package.json, removing the need for manual
git tags to publish new npm releases.

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

.github/workflows/publish.yml

@@ -2,14 +2,41 @@ name: Publish npm package
 
 on:
   push:
-    tags: ['v*']
+    branches: [main]
+    paths: ['napi/package.json']
 
 permissions:
   contents: read
   id-token: write
 
 jobs:
+  check-version:
+    name: Check version change
+    runs-on: ubuntu-latest
+    outputs:
+      changed: ${{ steps.check.outputs.changed }}
+      version: ${{ steps.check.outputs.version }}
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 2
+
+      - name: Check if version changed
+        id: check
+        run: |
+          NEW_VERSION=$(node -p "require('./napi/package.json').version")
+          OLD_VERSION=$(git show HEAD~1:napi/package.json | node -p "JSON.parse(require('fs').readFileSync('/dev/stdin','utf8')).version")
+          echo "old=$OLD_VERSION new=$NEW_VERSION"
+          if [ "$NEW_VERSION" != "$OLD_VERSION" ]; then
+            echo "changed=true" >> "$GITHUB_OUTPUT"
+            echo "version=$NEW_VERSION" >> "$GITHUB_OUTPUT"
+          else
+            echo "changed=false" >> "$GITHUB_OUTPUT"
+          fi
+
   build:
+    needs: check-version
+    if: needs.check-version.outputs.changed == 'true'
     name: Build ${{ matrix.target }}
     runs-on: ${{ matrix.os }}
     strategy:
@@ -68,7 +95,7 @@ jobs:
 
   publish:
     name: Publish to npm
-    needs: build
+    needs: [check-version, build]
     runs-on: ubuntu-latest
     permissions:
       contents: read