fix: auto-update dist folder in Renovate PRs via GitHub Actions

Replaces non-functional postUpgradeTasks configuration with a GitHub Actions
workflow that automatically rebuilds the distribution when Renovate opens PRs.

The previous approach used postUpgradeTasks and allowedCommands, which only
work with self-hosted Renovate. Since this repo uses GitHub's hosted Renovate
app, those settings were ignored, causing the dist folder to not be updated.

The new workflow:
- Triggers on PRs that modify package.json, package-lock.json, or src/
- Only runs for Renovate bot PRs
- Runs npm run all to rebuild dist/
- Commits and pushes changes back to the PR branch

This fixes the artifact update warnings in Renovate PRs like #294.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.github/workflows/renovate-dist-update.yml

@@ -0,0 +1,52 @@
+name: Update Distribution on Renovate PRs
+
+on:
+  pull_request:
+    paths:
+      - 'package.json'
+      - 'package-lock.json'
+      - 'src/**'
+      - 'tsconfig.json'
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  update-dist:
+    # Only run for Renovate PRs
+    if: github.actor == 'renovate[bot]' || github.actor == 'renovate-bot'
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout PR branch
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ github.head_ref }}
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Build and package
+        run: npm run all
+
+      - name: Check for changes
+        id: git-check
+        run: |
+          git diff --exit-code dist/ || echo "changed=true" >> $GITHUB_OUTPUT
+
+      - name: Commit and push changes
+        if: steps.git-check.outputs.changed == 'true'
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add dist/
+          git commit -m "chore: rebuild distribution"
+          git push