fix: worker stream state

[grutt]

Description

Fixes the case where a grpc stream is disrupted but heartbeats are still received.

Type of change

• [x] Bug fix (non-breaking change which fixes an issue)

What's Changed

• [x] adds an isActive flag to the worker record to
• [x] filters all valid_workers by is active to ensure that
• [x] if the grpc stream is not active, we reject heartbeats
• [x] reassign work to valid workers if it is stuck in the assigned state