AI Title Optimization: Add error handling for Title Optimization

[renatoagds]

Closes #36947

Proposed changes:

• Set a new error state to show a minimal message saying that an error occurred.
• Show Try Again button and message when error happens.
• Disable entry button if no content.

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

N/A

Does this pull request change what data or activity we track or use?

N/A

Testing instructions:

• Sandbox public-api and add an early error. Ex. return new \WP_Error( 'jetpack_ai_error', __( 'There was an error processing the completion request.' ), [ 'status' => 500 ] );
• Open your editor, if it has no content, the button should disabled.
• Ask for an title, it will fail and show the message.
• Clicking on Try Again will do a new request and show loading state again.

Demo

CleanShot.2024-05-02.at.17.26.58.mp4

[github-actions]

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Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen daily.
• WoA releases happen weekly.
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[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WordPress.com Simple site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin, and enable the add/title-optimization-error branch.

• To test on Simple, run the following command on your sandbox:

  bin/jetpack-downloader test jetpack add/title-optimization-error
  

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[dhasilva]

The error treatment works:

Before	After

I left a suggestion about the error message wording.