[issue #660] Add context-aware error message in Block Editor

[AshishJii]

What?

Closes #660

Implements a context-aware error message in the Block Editor's "Generate Title" flow when the AI connector is pending administrator authorization under the Connector Approvals screen.

Why?

Previously, when the Connector Approvals feature blocked the caller (wp-ai), the user was shown a generic error message: "Title generation failed. Please ensure you have a connected provider that supports text generation."
This led users to believe that their API keys or connected providers were broken when the feature was actually just awaiting approval in the WordPress admin panel.

Showing a clear, specific message helps the administrator locate and approve the pending connection under Tools > Connector Approvals.

How?

In includes/Abilities/Title_Generation/Title_Generation.php:

• Checked if the classes Approvals_Store and Caller_Identifier exist.
• Retrieved the caller details and searched the Approvals_Store for any pending requests matching the caller's basename (wp-ai).
• If a pending request is found, updated the fallback $error_message from the generic one to: "Title generation failed. The AI connector is currently pending authorization. Please approve the request under Tools > Connector Approvals."

Use of AI Tools

AI assistance: Yes
Tool(s): Gemini
Model(s): Gemini 3.5 Flash
Used for: Writing the Pull Request description.

Testing Instructions

1. Install the AI plugin and a provider plugin (e.g. Google).
2. Configure the API connection, but do not approve the caller yet in Tools > Connector Approvals.
3. Open a page/post and click "Generate Title".
4. Verify that the error message displays: "Title generation failed. The AI connector is currently pending authorization. Please approve the request under Tools > Connector Approvals."
5. Approve the connector under Tools > Connector Approvals.
6. Try generating a title again and verify it now succeeds without the error.

Screenshots or screencast

Before	After

Changelog Entry

Fixed - Display a clear, context-aware error notice during Title Generation when the AI connector is pending authorization.

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