feat(tasks): unify saved tasks on ssh_tasks services

- Add shared task_runner.run_saved_task helper used by routers/tasks.py and
  widgets/sources.py SshTaskWidgetSource.
- Saved tasks now target ssh_tasks service instances via default_service_id;
  the legacy default_machine_id and saved_task_runs are removed.
- Actions page lists ssh_tasks services for default and run-time selection.
- Update types, API client, hooks, tests, docs, and changelog.

Backend tests: 222 passed. Frontend lint/build/test: clean (71 passed).

frontend/src/test/setup.ts

@@ -23,3 +23,26 @@ globalThis.ResizeObserver =
 // Radix popper also probes `requestAnimationFrame`; jsdom provides it, but some
 // primitives defer layout reads through rAF that never flush in jsdom. Keep the
 // default rAF; this guard is intentionally minimal.
+
+// Radix Select uses pointer capture APIs that jsdom does not implement.
+// Stub them on HTMLElement so opening/closing selects in tests does not throw.
+if (typeof window !== "undefined" && window.HTMLElement) {
+	const proto = window.HTMLElement.prototype;
+	if (!proto.hasPointerCapture) {
+		proto.hasPointerCapture = () => false;
+	}
+	if (!proto.setPointerCapture) {
+		proto.setPointerCapture = () => {};
+	}
+	if (!proto.releasePointerCapture) {
+		proto.releasePointerCapture = () => {};
+	}
+}
+
+// Radix Select also calls scrollIntoView on items when opening; jsdom lacks it.
+if (typeof window !== "undefined" && window.Element) {
+	const proto = window.Element.prototype;
+	if (!proto.scrollIntoView) {
+		proto.scrollIntoView = () => {};
+	}
+}