Add Advanced Settings toggle to Developer Tools menu

[Infinite-Null]

What?

Part of #793

Adds a new "Advanced settings" option to the Developer Tools ellipses menu on the AI Settings page. When disabled, features only show their simple on/off toggle. When enabled, additional configuration options for a feature (e.g. Content Classification's taxonomy strategy and maximum suggestions) become visible.

Why?

The primary audience for the AI plugin is non-technical site owners. Previously, enabling a feature/experiment immediately exposed all of its advanced configuration options.

Note: Per discussion on #793, the Type Ahead additional settings (#151) are intentionally not being restored as part of this change.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude
Model(s): Claude Sonnet 4.5
Used for: Code review and refinement feedback during development.

Testing Instructions

1. Open the AI Settings page (/wp-admin/options-general.php?page=ai-wp-admin).
2. Click the vertical ellipses (Developer Tools) menu in the top right, confirm a new "Advanced settings" option appears below "Model selection," unchecked by default.
3. Enable a feature/experiment that has advanced settings (e.g. Content Classification), confirm no extra settings fields appear yet.
4. Open Developer Tools and click "Advanced settings" to enable it, confirm the feature's extra settings (e.g. Taxonomy strategy, Maximum suggestions) now appear inline.
5. Disable "Advanced settings" again, confirm those fields disappear
6. Reload the page, confirm the Advanced Settings preference persists.
7. Run the e2e suite: tests/e2e/specs/admin/settings.spec.js and tests/e2e/specs/experiments/content-classification.spec.js.

Screenshots or screencast

Screen.Recording.2026-07-07.at.4.59.07.PM.mov

Changelog Entry

Added - New "Advanced settings" option in Developer Tools to show/hide additional configuration options for features and experiments.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.04%. Comparing base (a993bbe) to head (c36edd5).

Additional details and impacted files

@@            Coverage Diff             @@
##             develop     #842   +/-   ##
==========================================
  Coverage      77.04%   77.04%           
  Complexity      2231     2231           
==========================================
  Files            103      103           
  Lines           9214     9214           
==========================================
  Hits            7099     7099           
  Misses          2115     2115           

Flag	Coverage Δ
unit	77.04% <ø> (ø)

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[github-actions]

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Co-authored-by: Infinite-Null <ankitkumarshah@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>

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