Use --bin flag for pkg.pr.new to show npx commands

This shows `npx` commands instead of `npm i` in PR preview comments,
which is more appropriate for this CLI tool.

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

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

Author: pcarleton

.github/workflows/pr-publish.yml

@@ -24,4 +24,4 @@ jobs:
       - name: Build
         run: npm run build
       - name: Publish
-        run: npx pkg-pr-new publish
+        run: npx pkg-pr-new publish --bin