kwargs: {} gets added to plan **kwargs

先从 prepare_params 和 _inner_prepare_params 引用的参数准备逻辑入手，然后检查 src/blueapi/worker/task.py 和 src/blueapi/worker/task_worker.py 中的执行路径。使用 Bluesky 的 abs_set 计划桩复现问题，并确认生成的调用不再包含 kwargs 项。当使用 *args 和 **kwargs 的计划执行时不再传入额外的 kwargs: {} 参数，即完成此 Issue。

When attempting to use a plan with *args and **kwargs, the current logic for prepare_params has a bug where it will provide additional kwargs like below:

2026-10-23 17:22:42,335     INFO blueapi.worker.task_worker Submitting: task_id='1ca72adb-8af4-42d5-8253-9ad6ba446699' task=Task(name='abs_set', args=['stage.x', 1.0], params={}, metadata={'user': 'alice', 'instrument_session': 'cm12345-1', 'tiled_access_tags': ['{"proposal": "cm12345", "visit": 1, "beamline": "adsim"}'], 'blueapi_task_id': '1ca72adb-8af4-42d5-8253-9ad6ba446699'}) request_id=None is_complete=False is_pending=True errors=[] outcome=None
2026-10-23 17:22:42,335     INFO blueapi.worker.task_worker Got new task: task_id='1ca72adb-8af4-42d5-8253-9ad6ba446699' task=Task(name='abs_set', args=['stage.x', 1.0], params={}, metadata={'user': 'alice', 'instrument_session': 'cm12345-1', 'tiled_access_tags': ['{"proposal": "cm12345", "visit": 1, "beamline": "adsim"}'], 'blueapi_task_id': '1ca72adb-8af4-42d5-8253-9ad6ba446699'}) request_id=None is_complete=False is_pending=True errors=[] outcome=None
2026-10-23 17:22:42,335     INFO blueapi.worker.task Asked to run plan abs_set with {} and metadata {'user': 'alice', 'instrument_session': 'cm12345-1', 'tiled_access_tags': ['{"proposal": "cm12345", "visit": 1, "beamline": "adsim"}'], 'blueapi_task_id': '1ca72adb-8af4-42d5-8253-9ad6ba446699'} for all runs
2026-10-23 17:22:42,336     INFO bluesky Executing plan <bluesky.utils.Plan object at 0x7f743a7a7880>
2026-10-23 17:22:42,336     INFO bluesky.RE.state Change state on <bluesky.run_engine.RunEngine object at 0x7f746c2ed940> from 'idle' -> 'running'
2026-10-23 17:22:42,337     INFO blueapi.service.main 127.0.0.1:46838 PUT /worker/task 200
2026-10-23 17:22:42,337    ERROR bluesky Run aborted
Traceback (most recent call last):
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 1596, in _run
    msg = self._plan_stack[-1].throw(stashed_exception or resp)
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/utils/__init__.py", line 2092, in __iter__
    return (yield from self._iter)
            ^^^^^^^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/plan_stubs.py", line 316, in abs_set
    ret = yield Msg("set", obj, *args, group=group, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 1688, in _run
    new_response = await coro(msg)
                   ^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/opentelemetry/util/_decorator.py", line 61, in async_wrapper
    return await func(*args, **kwargs)  # type: ignore
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 2278, in _set
    ret = obj.set(*msg.args, **kwargs)
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/ophyd_async/core/_status.py", line 289, in wrap_f
    return cls(f(*args, **kwargs), name=name)
               ~^^^^^^^^^^^^^^^^^
TypeError: StandardMovable.set() got an unexpected keyword argument 'kwargs'
2026-10-23 17:22:42,338     INFO bluesky.RE.state Change state on <bluesky.run_engine.RunEngine object at 0x7f746c2ed940> from 'running' -> 'idle'
2026-10-23 17:22:42,339    ERROR blueapi.worker.task_worker Task failed
2026-10-23 17:22:42,339    ERROR blueapi.worker.task_worker StandardMovable.set() got an unexpected keyword argument 'kwargs'
Traceback (most recent call last):
  File "/scratch/bluesky_development/blueapi/src/blueapi/worker/task_worker.py", line 436, in process_task
    result = self._current.task.do_task(self._ctx)
  File "/scratch/bluesky_development/blueapi/src/blueapi/worker/task.py", line 112, in do_task
    result = ctx.run_engine(plan(*prepared_args, **prepared_kwargs))
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 979, in __call__
    plan_return = self._resume_task(init_func=_build_task)
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 1127, in _resume_task
    raise exc
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 1767, in _run
    raise err
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 1596, in _run
    msg = self._plan_stack[-1].throw(stashed_exception or resp)
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/utils/__init__.py", line 2092, in __iter__
    return (yield from self._iter)
            ^^^^^^^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/plan_stubs.py", line 316, in abs_set
    ret = yield Msg("set", obj, *args, group=group, **kwargs)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 1688, in _run
    new_response = await coro(msg)
                   ^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/opentelemetry/util/_decorator.py", line 61, in async_wrapper
    return await func(*args, **kwargs)  # type: ignore
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/bluesky/run_engine.py", line 2278, in _set
    ret = obj.set(*msg.args, **kwargs)
  File "/scratch/bluesky_development/blueapi/.venv/lib/python3.13/site-packages/ophyd_async/core/_status.py", line 289, in wrap_f
    return cls(f(*args, **kwargs), name=name)
               ~^^^^^^^^^^^^^^^^^
TypeError: StandardMovable.set() got an unexpected keyword argument 'kwargs'

[Motor(name="stage-x"), 1.0] {'group': None, 'wait': False, 'kwargs': {}}

The dict is the kwargs, but _inner_prepare_params adds an additional kwargs: {} inside which causes a plan to fail

Steps to reproduce. Configure system tests to use bluesky plan stub abs_set. I originally discovered this when looking at https://github.com/DiamondLightSource/blueapi/pull/1694/

Acceptance Criteria

• second kwargs: () is not passed to the plan