- 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).
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