Add operation-local database handler bridge

[alexstandiford]

Summary

Adds the PHPNomad DB bridge for coordinated operations on database-backed datastore handlers.

• Clones handlers and providers without mutating shared provider state.
• Binds every local provider to the coordinator query strategy and validates exact shared cache, event, and logger policy.
• Provides a named provider-factory seam for adapter-owned resource-bound query and clause builders.
• Bypasses shared cache reads during the callback and buffers cache invalidation and events until confirmed commit.
• Discards local state on rollback and returns publication and logging failures after commit.
• Refuses attach and detach from inside the coordinated event strategy.

The design follows Siren CRM core (Source 9721), Coordinated database operations (Source 9774), Operation-local query boundary (Source 9775), and Retry-safe score projection (Source 9790).

Base and dependency

Base: release/2.2, after merged PR 37. This stays on the PHPNomad 2.2 line and does not depend on current-main identity work.

The adapter dependency is the named PHPNomad Database interface OperationDatabaseProviderFactory. The WordPress adapter must implement it with its pinned resource-bound query and clause builders before its handler callback begins. No adapter resource or global database state is used by this package.

Checks

• vendor/bin/phpunit passes: 172 tests, 521 assertions.
• PHPStan level 9 passes with the release/2.2 baseline and zero new findings.
• composer validate --strict passes.
• PHP lint and git diff --check pass.
• PHP CS Fixer dry-run passes for the new bridge files and focused tests.
• Hosted build-test, PHPStan, and spellcheck checks pass.

This is a draft because the adapter integrations still need to implement the named provider factory for their resource-bound builders.