Replay duplicate activity polls by poll_request_id

[rmcdaniel]

Fixes #5.

Summary

• accept poll_request_id on activity-task polls and coordinate duplicate requests through an activity poll-request cache
• replay only still-leased activity tasks and refresh cached payloads from live row state before redelivery
• add focused feature coverage for duplicate activity poll_request_id redelivery

Testing

• docker run --rm --network host -u 1000:1000 -e DB_CONNECTION=sqlite -e DB_DATABASE=/workspace/testbench.sqlite -e REDIS_HOST=127.0.0.1 -v /home/lab/workspace-hq/repos/server:/workspace -w /workspace composer:2 php ./vendor/bin/phpunit tests/Feature/WorkflowWorkerProtocolTest.php --filter poll_request