Module output_subscriber 

Build-event subscriber that dispatches every BuildEvent into the selected output-formatter plugin’s hm_output_on_event capability.

Replaces the plan-2 stop-gap stderr_sink. The subscriber acquires an Arc<LoadedPlugin> from the registry per event; the actual call_capability await happens AFTER the registry lock is dropped so concurrent step-executor invocations do not contend with it. Output plugins live in their own pool slot (default size 1) — only this one subscriber task drains the bus, so a pool of 1 suffices.

Functions

spawn

Spawn the subscriber task. Returns a join handle the orchestrator awaits at shutdown so the BuildEnd event is fully drained.