Abilities support: Add abilities for Field Groups

[priethor]

What

Part of #171

Adds WordPress Abilities API support for UI Field Groups, enabling AI assistants and external tools to manage options pages programmatically.

Why

Enables AI-powered workflows to create, read, update, delete, duplicate, import, and export Field Groups, maintaining consistency with the existing abilities implementation pattern.

How

Follows the same pattern as the other abilities

• Added SCF_Field_Group_Abilities class extending the base internal post type abilities
• Registered options pages abilities in the abilities integration class
• Added E2E tests covering all CRUD operations for options pages
• Excluded the abilities class from codecov, as it is only settings and the real execution happens in the base class

More granular abilities for managing individual fields might be updated later.

Testing Instructions

1. Activate the plugin and ensure WordPress 6.9 with Abilities API support
2. Install the MCP Adapter plugin
3. Create an application password
4. Use your favorite agent to connect to your site using the application password
5. List abilities, create a Field Group, duplicate it, update it, etc. through MCP

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 12.23%. Comparing base (8edf4ba) to head (66a06e8).

Additional details and impacted files

@@            Coverage Diff            @@
##              trunk     #289   +/-   ##
=========================================
  Coverage     12.23%   12.23%           
  Complexity     4287     4287           
=========================================
  Files           284      284           
  Lines         34690    34690           
=========================================
  Hits           4244     4244           
  Misses        30446    30446           

Flag	Coverage Δ
e2e	30.72% <ø> (ø)
javascript	2.60% <ø> (ø)
phpunit	7.57% <ø> (ø)

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[github-actions]

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Core Committers: Use this line as a base for the props when committing in SVN:

Props priethor.

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