Absorb fetch pipeline from AbstractMapper, remove style tests

[alganet]

Add concrete fetch() and fetchAll() to Mapper, absorbing the full SQL pipeline that was removed from AbstractMapper. All pipeline methods (createStatement, fetchHydrated, parseHydrated, fetchSingle, fetchMulti) are now private implementation details.

Remove all style tests and style entity stubs, naming convention tests and integration tests now live in Data with InMemoryMapper. MapperTest already covers typed entity fetch/persist with the default Standard style.

[Copilot]

Pull request overview

This PR relocates the SQL fetch pipeline into Respect\Relational\Mapper by adding concrete fetch() / fetchAll() implementations, and simplifies the test suite by removing per-style tests and moving inline stub entities into dedicated stub files.

Changes:

• Add Mapper::fetch() and Mapper::fetchAll() and make the underlying pipeline helpers private implementation details.
• Remove tests/Styles/* tests (style/integration coverage moved elsewhere per PR description).
• Extract inline test stub entities from MapperTest / DbTest into tests/Stubs/* and update dev autoload + tooling config accordingly.

Reviewed changes

Copilot reviewed 23 out of 23 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/Mapper.php	Introduces public fetch() / fetchAll() and internalizes statement/hydration/parsing helpers as private methods.
tests/MapperTest.php	Removes inline stub entity class definitions (now loaded from tests/Stubs).
tests/DbTest.php	Removes inline fetch stub classes (now loaded from tests/Stubs).
tests/Stubs/*	Adds dedicated stub entity classes used by the test suite (including OtherEntity/*).
tests/Styles/*.php	Removes style-specific tests from this repository.
composer.json	Updates autoload-dev PSR-4 mappings to include the new stub locations.
phpcs.xml.dist	Applies the Respect ruleset directly (previous deferrals removed) while keeping the tests variable-name exclusion.
phpstan.neon.dist	Removes an ignore rule for duplicate array keys (no longer needed with removed tests).

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