refactor: rename aim to upm and extract appimage module

crates/upm-core/tests/install_policy.rs

@@ -0,0 +1,49 @@
+use std::path::Path;
+use upm_core::integration::policy::{IntegrationMode, resolve_install_policy};
+use upm_core::platform::{DistroFamily, HostCapabilities, InstallScope};
+
+#[test]
+fn immutable_system_request_downgrades_to_user_when_allowed() {
+    let capabilities = HostCapabilities::immutable_user_only();
+    let policy =
+        resolve_install_policy(DistroFamily::Immutable, InstallScope::System, &capabilities)
+            .unwrap();
+
+    assert_eq!(policy.scope, InstallScope::User);
+    assert_eq!(policy.integration_mode, IntegrationMode::Degraded);
+    assert!(!policy.warnings.is_empty());
+}
+
+#[test]
+fn nix_system_request_is_denied() {
+    let error = resolve_install_policy(
+        DistroFamily::Nix,
+        InstallScope::System,
+        &HostCapabilities::default(),
+    )
+    .unwrap_err();
+
+    assert!(error.contains("not supported on Nix hosts"));
+}
+
+#[test]
+fn system_policy_uses_managed_payload_and_native_integration_roots() {
+    let policy = resolve_install_policy(
+        DistroFamily::Fedora,
+        InstallScope::System,
+        &HostCapabilities::default(),
+    )
+    .unwrap();
+
+    assert_eq!(policy.scope, InstallScope::System);
+    assert_eq!(policy.payload_root, Path::new("/opt/upm/appimages"));
+    assert_eq!(
+        policy.desktop_entry_root,
+        Path::new("/usr/share/applications")
+    );
+    assert_eq!(
+        policy.icon_root,
+        Path::new("/usr/share/icons/hicolor/256x256/apps")
+    );
+    assert_eq!(policy.integration_mode, IntegrationMode::Full);
+}