Add Android APK fleet nodes with Crucible UI integration and tests.

APK wrapper registers platform=android via AETHERFORGE_PLATFORM; fleet UI shows robot icons, Android Access Depth probes, and a shortened mining onion timeline.

agent/config/platform_test.go

@@ -0,0 +1,34 @@
+package config
+
+import (
+	"runtime"
+	"testing"
+)
+
+func TestRegistrationPlatformDefault(t *testing.T) {
+	t.Setenv("AETHERFORGE_PLATFORM", "")
+	if got := RegistrationPlatform(); got != runtime.GOOS {
+		t.Fatalf("RegistrationPlatform() = %q want %q", got, runtime.GOOS)
+	}
+	if IsAndroidPlatform() {
+		t.Fatal("IsAndroidPlatform() true without override")
+	}
+}
+
+func TestRegistrationPlatformFromEnv(t *testing.T) {
+	t.Setenv("AETHERFORGE_PLATFORM", "android")
+	if got := RegistrationPlatform(); got != "android" {
+		t.Fatalf("RegistrationPlatform() = %q want android", got)
+	}
+	if !IsAndroidPlatform() {
+		t.Fatal("IsAndroidPlatform() false with AETHERFORGE_PLATFORM=android")
+	}
+}
+
+func TestRegistrationPlatformApkMode(t *testing.T) {
+	t.Setenv("AETHERFORGE_PLATFORM", "")
+	cfg := RuntimeConfig{BuiltinConfig: BuiltinConfig{ApkMode: true}}
+	if got := cfg.RegistrationPlatform(); got != "android" {
+		t.Fatalf("RegistrationPlatform() = %q want android", got)
+	}
+}