Added umu download and repair for missing components on install, update and manual repair.

ptlinux/paths.py

@@ -71,6 +71,23 @@ class AppPaths:
 	def downloads(self) -> Path:
 		return self.cache / "downloads"
 
+	@property
+	def runtime_tools(self) -> Path:
+		"""Launcher-managed helpers that are independent of app releases."""
+
+		return self.data / "runtime-tools"
+
+	@property
+	def managed_umu_executable(self) -> Path:
+		return self.runtime_tools / "bin/umu-run"
+
+	@property
+	def managed_umu_metadata(self) -> Path:
+		return self.state / "umu-launcher.json"
+
+	def managed_umu_archive(self, version: str) -> Path:
+		return self.downloads / f"umu-launcher-{version}-zipapp.tar"
+
 	@property
 	def app_home(self) -> Path:
 		"""Stable home containing versioned native-launcher releases."""