chore: Add unit tests for MediaSharing and REST modules - Phase 3

[sabbir1991]

What

Adds unit test coverage for the OneMedia MediaSharing and REST modules.

Why

This PR improves PHPUnit coverage for recently added MediaSharing and REST functionality, focusing on safe unit-testable paths and keeping the same test style used in the previous unit testing phases.

Related Issue(s):

• Part of unit test coverage improvements for OneMedia.

How

This PR adds and expands PHPUnit tests for:

• MediaSharing admin hook registration and safe admin output paths.
• MediaSharing attachment sync status, version, and health-check validation behavior.
• MediaSharing UI sync column rendering and row action filtering.
• MediaSharing media protection edit/delete guard behavior.
• MediaSharing media action helper methods and invalid request handling.
• Media replacement behavior for post content and attachment metadata.
• REST permission handling in the abstract REST controller.
• Basic options REST controller settings behavior.
• Media sharing REST controller validation and local metadata/update branches.

The tests avoid remote sync, upload, and AJAX exit-heavy success paths, and use WordPress test helpers/factories where possible.

Testing Instructions

1. Check out this branch.

2. Start the test environment with coverage enabled:

   npm run wp-env:test -- start --xdebug=coverage

3. Run the PHP test suite:

   npm run test:php

4. Start the default wp-env environment if needed for linting:

   npm run wp-env -- start

5. Run PHP linting:

   npm run lint:php

Expected result:

• PHPUnit passes successfully.
• PHP linting passes successfully.

Screenshots

N/A. This PR only adds automated test coverage.

Additional Info

Last verified locally:

• npm run test:php
  • Passed: 153 tests, 257 assertions
• npm run lint:php
  • Passed: 50 / 50 (100%)
  • This PR depends on chore/php-unit-testing-phase-2 this branch so I set this PR base branch to chore/php-unit-testing-phase-2. once this PR chore: Add unit tests for media and settings modules - phase 2 #130 merged we need to reabse the main branch with current PR branch

Checklist

• I have read the Contribution Guidelines.
• I have read the Development Guidelines.
• My code is tested to the best of my abilities.
• My code passes all lints (ESLint etc.).
• My code has detailed inline documentation.
• I have updated the project documentation as needed.
• I have added a changeset for this PR using npm run changeset.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 39.41%. Comparing base (b6f74f0) to head (d57e30b).

Additional details and impacted files

@@                          Coverage Diff                          @@
##             chore/php-unit-testing-phase-2     #137       +/-   ##
=====================================================================
+ Coverage                             17.97%   39.41%   +21.43%     
  Complexity                              666      666               
=====================================================================
  Files                                    22       22               
  Lines                                  2748     2748               
=====================================================================
+ Hits                                    494     1083      +589     
+ Misses                                 2254     1665      -589     

Flag	Coverage Δ
unit	39.41% <ø> (+21.43%)	⬆️

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