Add filter hooks for AJAX suggest results

[apermo]

Summary

• Add msls_meta_box_suggest_results and msls_post_tag_suggest_results filters on the final suggest results array, enabling add-on plugins to re-sort, relabel, insert spacers, or reorder translation candidates
• Pass source_id (the post/term being edited) through JS AJAX request and into the filter context, so consumers can implement heuristic matching
• New FIELD_SOURCE_ID constant in MslsFields with hidden field in both post metabox and term input templates

Closes #604

Test plan

• All 400 existing tests pass
• New tests verify both filters are applied with correct context
• Manual: hook into msls_meta_box_suggest_results, confirm modified results appear in autocomplete dropdown

[gemini-code-assist]

Code Review

This pull request introduces a 'source_id' field to the post and term suggestion functionality within the Multisite Language Switcher. Key changes include the addition of a new constant in MslsFields, the inclusion of a hidden 'msls_source_id' input in meta boxes and tag edit screens, and an update to the AJAX logic in msls.js to transmit this ID. Furthermore, two new filters, 'msls_meta_box_suggest_results' and 'msls_post_tag_suggest_results', have been implemented to allow for the modification of suggestion results before they are returned. Corresponding unit tests have been updated to reflect these enhancements. I have no feedback to provide as there were no review comments to evaluate.

[apermo]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a new source_id field to the suggestion logic for both posts and terms within the Multisite Language Switcher. Key changes include the addition of a FIELD_SOURCE_ID constant, the inclusion of hidden input fields in the meta box and post tag interfaces to track the source ID, and updates to the AJAX request in msls.js to transmit this value. Furthermore, new WordPress filters (msls_meta_box_suggest_results and msls_post_tag_suggest_results) have been implemented to allow for the modification of suggestion results before they are returned. Corresponding PHPUnit tests have been updated to verify these enhancements. I have no feedback to provide as there were no review comments to evaluate.

[apermo]

Verified locally with the following mu plugin:

<?php                                                                                                                
  /**                                                                                               
   * Plugin Name: MSLS Suggest Shuffle                                                                                 
   * Description: Shuffles MSLS suggest results in seeded random order and stars the first two.
   */                                                                                                                  
                                                                                                    
  add_filter( 'msls_meta_box_suggest_results', 'msls_suggest_shuffle', 10, 2 );                                        
  add_filter( 'msls_post_tag_suggest_results', 'msls_suggest_shuffle', 10, 2 );
                                                                                                                       
  /**                                                                                               
   * Shuffle suggest results using the source post ID as seed and prepend stars to the first two.
   *                                                                                                                   
   * @param array<int, array{value: int, label: string}> $results
   * @param array<string, mixed>                         $context                                                      
   *                                                                                                                   
   * @return array<int, array{value: int, label: string}>
   */                                                                                                                  
  function msls_suggest_shuffle( array $results, array $context ): array {                          
        if ( empty( $results ) ) {    
                return $results;                                                                                       
        }
                                                                                                                       
        $source_id = (int) ( $context['source_id'] ?? 0 );                                          
        mt_srand( $source_id );       
        shuffle( $results );
        mt_srand();                                                                                                    
  
        foreach ( array_slice( array_keys( $results ), 0, 2 ) as $key ) {                                              
                $results[ $key ]['label'] = '⭐ ' . $results[ $key ]['label'];                      
        }                             
                                                                                                                       
        return $results;
  }     

[lloc]

This looks good to me.