chore: test flake: TestCoderLog

```
--- FAIL: TestCoderLog (0.00s)
--- FAIL: TestCoderLog/OutputNotDropped (0.01s)
coder_test.go:100:
Error Trace: /home/runner/work/envbox/envbox/buildlog/coder_test.go:100
Error: Condition never satisfied
Test: TestCoderLog/OutputNotDropped
--- FAIL: TestCoderLog/OK (0.01s)
coder_test.go:51:
Error Trace: /home/runner/work/envbox/envbox/buildlog/coder_test.go:51
Error: Condition never satisfied
Test: TestCoderLog/OK
FAIL
```

I could only get it to reproduce somewhat reliably by running

```
go test -count=10000 ./buildlog/
```

Interestingly, the race detector didn't seem to pick anything up.

Comienza con buildlog/coder_test.go, especialmente con TestCoderLog/OK y TestCoderLog/OutputNotDropped, y reproduce el fallo con go test -count=10000 ./buildlog/. Investiga por qué no se cumplen las condiciones y verifica que ambas subpruebas pasen de forma fiable cuando se resuelva el flake.

Escrito por el modelo de indexación a partir del texto del issue.