fix(testrun): an ios run records the simulator it executed on

Device was read from --device, which only an android run sets, so every
ios meta.json left the field empty and the trace could not say what
hardware produced it.

internal/testrun/testrun.go

@@ -90,6 +90,15 @@ type Options struct {
 // recorded only when the LLM picker is the one that will actually run, so a
 // spec that declares generator = llm() but is run under the seeded picker does
 // not label its trace with a model it never called.
+// runDevice reads whichever flag named the hardware for this platform. An ios
+// run is selected with --ios-device and leaves --device empty.
+func runDevice(options Options) string {
+	if options.Platform == "ios" {
+		return options.IosDevice
+	}
+	return options.Device
+}
+
 func buildRunMeta(options Options, bundleSHA256 string, seed int64, host string, llmConfig verifier.LLMConfig, hasLLMConfig bool) trace.Meta {
 	meta := trace.Meta{
 		Seed:              seed,
@@ -105,7 +114,7 @@ func buildRunMeta(options Options, bundleSHA256 string, seed int64, host string,
 		MaxSteps:          options.MaxSteps,
 		DurationMillis:    options.Duration.Milliseconds(),
 		Host:              host,
-		Device:            options.Device,
+		Device:            runDevice(options),
 	}
 	if options.Generator == "llm" && hasLLMConfig {
 		meta.Model = llmConfig.Model

internal/testrun/testrun_test.go

@@ -282,6 +282,36 @@ func TestBuildRunMeta_RecordsLabelSourceForASeededRun(t *testing.T) {
 	}
 }
 
+// An ios run names its simulator with --ios-device, so reading the android
+// --device flag left every ios trace unable to say what it executed on.
+func TestBuildRunMeta_NamesTheIosSimulatorItRanOn(t *testing.T) {
+	options := Options{
+		Platform:  "ios",
+		Generator: "seeded",
+		Duration:  time.Minute,
+		IosDevice: "iPhone 17 Pro",
+	}
+	meta := buildRunMeta(options, "deadbeef", 1, "farm-01", verifier.LLMConfig{}, false)
+
+	if meta.Device != "iPhone 17 Pro" {
+		t.Errorf("device: got %q, want the ios simulator the run named", meta.Device)
+	}
+}
+
+func TestBuildRunMeta_NamesTheAndroidDeviceItRanOn(t *testing.T) {
+	options := Options{
+		Platform:  "android",
+		Generator: "seeded",
+		Duration:  time.Minute,
+		Device:    "emulator-5554",
+	}
+	meta := buildRunMeta(options, "deadbeef", 1, "farm-01", verifier.LLMConfig{}, false)
+
+	if meta.Device != "emulator-5554" {
+		t.Errorf("device: got %q, want the android device the run named", meta.Device)
+	}
+}
+
 func TestBuildRunMeta_OmitsModelWhenSpecDeclaresNoLLMGenerator(t *testing.T) {
 	options := Options{Platform: "android", Generator: "llm", Duration: time.Minute}
 	meta := buildRunMeta(options, "deadbeef", 1, "farm-01", verifier.LLMConfig{}, false)