[issue #660] feat: Update generalised error message for all features

[SohamPatel46]

What?

Closes #660

Implements a centralized, context-aware error message mapping in the WordPress REST API when AI requests (e.g. "Generate Title", "Generate Excerpt") are blocked by the Connector Approvals feature.

Why?

Previously, when the Connector Approvals feature blocked the caller (wp-ai), the user was shown a generic error notice: "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.

Using a centralized server-side approach via a REST dispatch filter ensures that all features display clean, translated, and context-aware instructions explaining how to authorize the connector under Tools > Connector Approvals, without duplicating approval-checking code across individual feature controllers or frontend JS files.

How?

1. REST Error Customizer:
   • Registered the rest_post_dispatch filter inside the Connector_Approval experiment class.
   • If a REST request fails with the wpai_connector_not_approved code, it intercepts the error, parses the Ability ID from the route path, and maps it to a context-aware prefix (e.g. "Title generation failed.", "Excerpt generation failed.").
   • Appends: "The AI connector is currently pending authorization. Please approve the request under Tools > Connector Approvals."
2. Capability Check Fallback:
   • Updated ensure_text_generation_supported() and ensure_image_generation_supported() in Abstract_Ability.
   • If the remote model fetch requests get blocked by the approvals check during capability check, it now falls back to return wpai_connector_not_approved instead of the generic unsupported_model error.

Use of AI Tools

• AI assistance: Yes
• Tool(s) used: Antigravity IDE.
• Model(s) used: Gemini 3.5 Flash
• Used for: Suggestion for designing the centralized server-side solution, code refactoring, test case additions. Implementation was reviewed, modified and tested by me.

Testing Instructions

1. Install the AI plugin and configure an AI provider (e.g., Google Connector), but do not approve the caller under Tools > Connector Approvals yet.
2. Open a page/post and click Generate Title.
3. Verify that the notice displays: "Title generation failed. The AI connector is currently pending authorization. Please approve the request under Tools > Connector Approvals."
4. Click Generate Excerpt (if excerpt generation experiment is active) and verify it displays: "Excerpt generation failed. The AI connector is currently pending authorization. Please approve the request under Tools > Connector Approvals."
5. Go to Tools > Connector Approvals and approve the connector.
6. Return to the post editor and verify that title and excerpt generation now succeed without the error.

Screenshots or screencast

Before	After

Changelog Entry

Fixed - Display a clear, context-aware error notice during Ability execution when the configured AI connector is pending administrator approval.

Added - New feature.
Changed - Existing functionality.
Deprecated - Soon-to-be removed feature.
Removed - Feature.
Fixed - Bug fix.
Security - Vulnerability.
Developer - Development related updates.

[github-actions]

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Co-authored-by: SohamPatel46 <sohampate1@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: riccardodicurti <riccardodicurti@git.wordpress.org>

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[codecov]

Codecov Report

❌ Patch coverage is 97.61905% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 75.79%. Comparing base (9db55ee) to head (3cd5918).

Files with missing lines	Patch %	Lines
includes/Abstracts/Abstract_Ability.php	92.30%	2 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #759      +/-   ##
=============================================
+ Coverage      75.50%   75.79%   +0.29%     
- Complexity      2086     2117      +31     
=============================================
  Files             99       99              
  Lines           8626     8710      +84     
=============================================
+ Hits            6513     6602      +89     
+ Misses          2113     2108       -5     

Flag	Coverage Δ
unit	75.79% <97.61%> (+0.29%)	⬆️

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[dkotter]

All @since statements need to be set to x.x.x