Add triggers to .github/workflows/

[cartland]

This PR standardizes GitHub Actions triggers in workflow files within .github/workflows/.

The goal is to ensure workflows run consistently on push, pull_request, and workflow_dispatch events where appropriate.

This is part of a batch of pull requests across repositories owned by the android organization on GitHub.

Project Owner: Please review the changes carefully to ensure they are correct and appropriate for this project before approving and merging.

• If you do not think this change is appropriate (e.g., a workflow should NOT run on one of these triggers), please leave a comment explaining why.
• If you think the goal is appropriate but notice a mistake in the implementation, please leave a comment detailing the mistake.

[gemini-code-assist[bot]]

[!NOTE] The files in this pull request are not supported by Gemini Code Assist.