feat(search-ordering): allow removing posts from custom search results

[faisalahammad]

Summary

Added ability to remove individual posts from a custom search result.
Excluded posts are now stored and filtered out from the final search results for that query.
Fixes #4245

Changes

Frontend (assets/js/ordering/pointers.js)

Before:

removePointer(pointer) {
    // Only removed reordered default results via removedPointers.
}

After:

removePointer(pointer) {
    if (pointer.type === 'custom-result') {
        excludedPosts.push(pointer.ID);
    } else {
        removedPointers.push(pointer.ID);
    }
    // Updates state and hidden input excluded_posts
}

Why: Differentiates between custom-added results (should be excluded) and reordered defaults (should be returned to original position).

Backend (includes/classes/Feature/SearchOrdering/SearchOrdering.php)

Before:

function save_post($post_id) {
    // Saved pointers only.
}
function posts_results($posts) {
    // Injected custom results but did not filter any posts.
}

After:

function save_post($post_id) {
    // Now reads $_POST['excluded_posts'], sanitizes, and stores in post meta 'excluded_posts'.
    // Clears excluded list when search term changes.
}
function posts_results($posts) {
    // After injecting custom results, fetches excluded list and removes those posts from results.
}

Why: Persists the exclusion list per custom search result and applies it to query results.

Tests (tests/php/features/TestSearchOrdering.php)

Added three new PHPUnit tests:

• testSavePostWithExcludedPosts
• testPostsResultsFiltersExcludedPosts
• testExcludedPostsClearedOnSearchTermChange

Testing

Test 1: Exclude a post from a custom search result

1. Create a custom search result for "example".
2. Add a post to the result.
3. Click the trash icon on the added post.
4. Save the custom search result.
5. Search for "example" on the frontend.
   Result: The excluded post does not appear in the search results.

Test 2: Automated tests pass
Run composer run test --filter TestSearchOrdering.
Result: All tests pass.