chore: switch release-please to tag-based versioning

[google-labs-jules]

The release-please workflow was previously configured to use a manifest file as the source of truth for versioning. This caused synchronization issues where the manifest could lag behind existing Git tags (e.g., manifest at 1.2.1 while tag v1.2.2 exists), leading to failed or incorrect release attempts.

This change simplifies the workflow by:

1. Deleting .release-please-manifest.json and release-please-config.json.
2. Configuring .github/workflows/release-please.yml to use release-type: simple and update version.txt directly.

This ensures release-please now relies on Git tags as the single source of truth, preventing future version mismatches.

---

PR created automatically by Jules for task 4138685454215998593 started by @azman0101

[google-labs-jules]

👋 Jules, reporting for duty! I'm here to lend a hand with this pull request.

When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down.

I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job!

For more direct control, you can switch me to Reactive Mode. When this mode is on, I will only act on comments where you specifically mention me with @jules. You can find this option in the Pull Request section of your global Jules UI settings. You can always switch back!

---

For security, I will only act on instructions from the user who triggered this task.

New to Jules? Learn more at jules.google/docs.

[semanticdiff-com]

Review changes with  

Changed Files

File	Status
.github/workflows/release-please.yml	41% smaller
.release-please-manifest.json	0% smaller
release-please-config.json	0% smaller