Make image generation request timeout configurable

[ishitaj34]

What?

Closes #853

This PR makes the request timeout for the image generation ability configurable via the wp_ai_client_default_request_timeout filter, while retaining 90 seconds as the default timeout.

Why?

The timeout was hardcoded to 90 seconds which completely bypassed the wp_ai_client_default_request_timeout global filter, meaning developers could not customise or extend the timeout for slower image generation requests.

How?

• Replaced hardcoded $request_options->setTimeout( 90 ) call with a filtered value:

$request_options->setTimeout( apply_filters( 'wp_ai_client_default_request_timeout', 90 ) )

• Added integration tests test_request_timeout_defaults_to_90 and test_request_timeout_can_be_filtered to verify the defaults and overridden filter values.
• Created a helper subclass Testable_Generate_Image to bypass environment checks so the tests can run anywhere.

Use of AI Tools

AI assistance: Yes
Tool(s): Gemini 3.5 Flash)
Used for: Drafting integration test assertions and preparing validation commands.

Testing Instructions

Run the automated tests:

npm run test:php -- --filter=Image_GenerationTest

Changelog Entry

Changed - Make image generation request timeout configurable via the wp_ai_client_default_request_timeout filter.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.43%. Comparing base (8c3606a) to head (e9d79e5).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #862      +/-   ##
=============================================
+ Coverage      78.40%   78.43%   +0.03%     
  Complexity      2454     2454              
=============================================
  Files            104      104              
  Lines           9918     9920       +2     
=============================================
+ Hits            7776     7781       +5     
+ Misses          2142     2139       -3     

Flag	Coverage Δ
unit	78.43% <100.00%> (+0.03%)	⬆️

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Co-authored-by: ishitaj34 <ishitaj34@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: jonathanbossenger <psykro@git.wordpress.org>

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