feat(trace): record the device a run executed on

meta.json carried the host but not the device, so a trace could not say what
hardware produced it without the campaign manifest beside it. An experiment
splitting cells across api levels could only join them through that manifest.

Claude-Session: https://claude.ai/code/session_01A5KmftdEJ49A9z5mF5ESrX

internal/testrun/testrun.go

@@ -102,6 +102,7 @@ func buildRunMeta(options Options, bundleSHA256 string, seed int64, host string,
 		MaxSteps:          options.MaxSteps,
 		DurationMillis:    options.Duration.Milliseconds(),
 		Host:              host,
+		Device:            options.Device,
 	}
 	if options.Generator == "llm" && hasLLMConfig {
 		meta.Model = llmConfig.Model