4.20.0

Included commits: 4.19.4...4.20.0

Improvements

• Extended SessionClient to degrade gracefully when no session container is registered — all methods now return neutral values (false, '', [], null) instead of failing, enabling applications such as the Storefront API, console commands, and queue workers to use SessionClient without bootstrapping a session.
• Updated SessionClientInterface::start() specification to document that it returns false when no session container is present.