Repair datastore prerequisites and add identity projection

[alexstandiford]

Summary

• declare phpnomad/event:^1.0, which public datastore event classes use at runtime
• remove obsolete private SSH setup because every locked dependency installs over public HTTPS
• let Composer and Packagist derive the library version
• update the vulnerable PHPUnit and Symfony Process development dependency closure while retaining PHP 7.4 compatibility
• add legitimate current README vocabulary to the spellcheck dictionary
• add the storage-neutral DatastoreHasIdentityQuery optional capability with grouped-condition, identity, limit, and zero-based offset shapes
• preserve the legacy WithDatastorePrimaryKeyDecorator::findIds() seam while refusing unsupported handlers with a clear LogicException
• add a narrow PHPStan baseline for the 31 findings already present on the dependency and CI prerequisite parent

Verification

• strict Composer validation passes
• Composer audit reports no advisories
• PHPUnit: 3 tests, 5 assertions on PHP 8.3 and PHP 7.4
• configured full lib and tests PHPStan level 9: 0 errors with the 31-entry legacy baseline
• focused PHPStan level 9 for the identity-query interface, decorator, and proof fixtures: 0 errors without the baseline
• a deliberate new identity-query return-type error is still reported by configured PHPStan, proving the baseline does not hide new defects
• removing the optional-capability guard makes the unsupported-handler regression fail while the supported delegation case remains green
• diff check passes

The runtime dependency resolves to phpnomad/event 1.0.1 at b418d8fc90af18b7cb37e118795f9dd92ffeb538.

The baseline contains only the 31 unchanged legacy findings from the prerequisite parent. It has no entries for the new interface, touched decorator, or proof fixtures.

This PR remains a draft. It does not merge or release the package.