Deduplicate indexing filters via a data-provider membership check

[loevgaard]

Closes #178.

Problem

"What should be indexed" lived in two parallel mechanisms that had to be kept in sync by hand:

1. Query-builder (SQL) filters (EventSubscriber/IndexableDataFilter/*) — shape a full reindex, applied inside DefaultIndexableDataProvider::getIds().
2. Object filters (Filter/Entity/*) — applied per entity in DefaultIndexer::indexEntities(), on both the batch and the incremental path.

EnabledEntityFilter/StockAvailableEntityFilter/ChannelsAwareEntityFilter mirrored the SQL filters so the same rules also applied on the incremental (Doctrine-event) path, where the query builder never runs. If a SQL/PHP pair diverged, batch and incremental disagreed about what qualifies — and since the incremental path issues deleteDocuments on filter-out, a divergence could delete a document a reindex would keep.

Solution

Route the incremental path through the same data provider the batch path uses, making the query-builder filters the single source of truth.

• IndexableDataProviderInterface gains containsId(string $entity, Index $index, int|string $id): bool.
• DefaultIndexableDataProvider builds its query once in a private createQueryBuilder() shared by getIds() and containsId(). The id constraint is added after the QueryBuilderForDataProvisionCreated dispatch, so every filter subscriber sees the identical query on both paths — that's what keeps them consistent.
• IndexEntityHandler asks containsId() whether a changed entity still qualifies for each index: index it if so, removeEntity() (delete its document) if not.

Only the two true mirrors are removed (EnabledEntityFilter, StockAvailableEntityFilter) along with their object-filter registrations in the extension. ChannelsAwareEntityFilter (per-scope channel membership — the SQL twin only checks SIZE(channels) > 0) and FilterableEntityFilter (arbitrary user FilterableInterface) stay. EntityFilterInterface remains the documented escape hatch for rules that can't be expressed in SQL or that depend on the channel/locale/currency scope.

BC breaks (pre-1.0)

• New method on IndexableDataProviderInterface — custom data providers must implement containsId().
• Filter\Entity\EnabledEntityFilter and Filter\Entity\StockAvailableEntityFilter are removed.

Notes

• Trade-off: the incremental path now runs one small indexed WHERE id = ? query per change per index instead of a purely in-memory check.
• Eventual consistency is unchanged: indexing runs through Messenger, so a document can briefly lag its entity — documented in the README.

Tests / QA

• New IndexEntityHandlerTest (index-when-contained, remove-when-not, not-found, non-scalar id).
• New DefaultIndexableDataProviderTest (functional): proves getIds()/containsId() agree and that disabling a product flips containsId() to false.
• Deleted the two mirror-filter unit tests with their classes.
• Green: ECS, PHPStan (level max, no baseline), Rector dry-run, composer validate --strict, composer normalize --dry-run, lint:container, Unit (111) and Functional (17) suites.
• End-to-end smoke (throwaway test, since removed): disabling a fixture product through the ORM fired the Doctrine listener, removed its document from Meilisearch, and re-enabling re-indexed it.

[codecov]

Codecov Report

❌ Patch coverage is 42.85714% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 49.03%. Comparing base (a615526) to head (c363346).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/DataProvider/DefaultIndexableDataProvider.php	0.00%	12 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #179      +/-   ##
============================================
- Coverage     49.08%   49.03%   -0.05%     
+ Complexity      805      798       -7     
============================================
  Files           139      137       -2     
  Lines          2557     2541      -16     
============================================
- Hits           1255     1246       -9     
+ Misses         1302     1295       -7     

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