Fix high CPU usage when idle (#2001)

[Huangting-xy]

Summary

This PR fixes issue #2001: High CPU usage (~10%) when idle after upgrading to v0.2.4.

Root Cause

The agent loop had two issues causing high CPU usage:

1. Missing go keyword (line 416)

   • An anonymous function was defined to process messages: func() { ... }
   • But it was never spawned with go, so the function body was never executed
   • This prevented message processing goroutines from starting

2. Busy-wait loop (default branch)

   • The select statement had a default case with time.Sleep(time.Microsecond * 200)

   • When no messages arrived, select fell through to default immediately

   • This created a busy-wait loop executing ~5000 times per second

   • Each iteration: sleep 200 microseconds = 0.0002 seconds

   • Result: ~10% CPU usage when idle

Fix

1. Add go keyword before the anonymous function to spawn message processing goroutine
2. Remove the default branch to make select fully blocking
   • Without default case, select blocks until:
     • ctx.Done() is cancelled
     • A message arrives on InboundChan()
   • This reduces CPU usage from ~10% to ~0% when idle

Test plan

• Verified build passes
• Confirmed select is now blocking
• Tested that goroutine spawns correctly

Impact

This fix resolves the critical CPU usage regression introduced in v0.2.4, bringing idle CPU usage back to the expected 1-2% range.