PHP SDK 2.3.7

Fix cooperative workers stopping valid slow external payload downloads after five seconds.

Worker presence, workflow lease renewal and activity ownership observation continue during bounded payload loading. Control calls keep their short bounds. Query leases, original cancellation deadlines, explicit request budgets and publication fencing remain enforced.

The default supervised download timeout is 30 seconds. Applications can select a finite larger timeout with Psr18Transport(payloadTransferTimeoutSeconds: 180). Integrity and authorization checks still run before application dispatch.

This is a compatible correction on the 2.3 stable line and excludes pending Nexus features from main.

Source and stable qualification: #151, #152. Normal installed consumers and the affected Sample tuple follow publication under #150/#146.