fix: remove dead Algolia filter and restrict search response payload / Algolia検索の無駄なフィルタ・レスポンス削減

[zigzagdev]

Motivation / 目的

An investigation into the search implementation found two low-risk, no-behavior-change cleanups in AlgoliaWorldHeritageSearchAdapter. Both were verified directly against the live (dev) Algolia index before fixing.

検索実装の調査で、AlgoliaWorldHeritageSearchAdapterに挙動を変えない低リスクな無駄を2件見つけました。修正前に実際のAlgoliaインデックス（dev用）に対してクエリを投げて事実確認しています。

What I have done / 実施内容

• Removed the state_party:"..." clause from buildCountryOrFilter(). state_party is never indexed (confirmed: AlgoliaImportWorldHeritages never pushes such a field), and querying it directly against the live index returns 0 hits with no error — it's dead weight sent on every country-name search.
• Added attributesToRetrieve: ['objectID', 'id'] to the searchSingleIndex call. Only the id is ever read from the response (WorldHeritageQueryService::searchHeritages re-fetches the full record from MySQL via findByIdsPreserveOrder), so the rest of each hit's fields were fetched from Algolia and immediately discarded.

Test Results / テスト結果

• test_search_builds_algolia_params_with_filters_and_paging
• test_search_by_country_name_without_iso3_does_not_filter_on_state_party

Full WorldHeritage-related suite (64 tests) also re-run with no regressions.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 64.99%. Comparing base (905138c) to head (1b88f2e).

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #577      +/-   ##
============================================
+ Coverage     64.66%   64.99%   +0.33%     
- Complexity     1694     1695       +1     
============================================
  Files           147      147              
  Lines          8858     8894      +36     
============================================
+ Hits           5728     5781      +53     
+ Misses         3130     3113      -17     

Files with missing lines	Coverage Δ
...tage/Adapter/AlgoliaWorldHeritageSearchAdapter.php	84.70% <100.00%> (+20.00%)	⬆️
...ge/Tests/AlgoliaWorldHeritageSearchAdapterTest.php	100.00% <100.00%> (ø)

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