Publish stable worker protocol contracts for embedded deployments #128
Description
Summary
Embedded adopters need a versioned worker protocol surface from Arco instead of reimplementing dispatch and callback contracts downstream.
Severity: high
Downstream evidence
We had to locally recreate:
- task envelope types
- started, heartbeat, and completed payloads
- heartbeat control responses
- task outcome and run status enums
- stable attempt ID helpers
Requested outcome
- Publish canonical serializable worker protocol types in an upstream crate or module
- Document header and auth expectations plus compatibility guarantees
- Add golden JSON fixtures or compatibility tests for the wire contract
- Provide minimal client and server examples for embedded orchestrator and worker setups
Why upstream
This is core Arco orchestration behavior. Leaving it to each integrator creates drift and makes upgrades risky.