fix(asyncio): make RunningCommand hashable for asyncio.gather (#800)

[ansh-rohilla]

Summary

RunningCommand defines __eq__ (return id(self) == id(other)), but did not define __hash__. In Python 3, overriding __eq__ without explicitly defining __hash__ implicitly sets __hash__ = None, making instances unhashable.

Because RunningCommand implements __await__, instances are commonly passed to asyncio.gather(*commands). However, asyncio.gather uses an internal dictionary lookup (arg not in arg_to_fut), which raised:

TypeError: unhashable type: 'RunningCommand'

Following the Python data model convention for classes with identity equality, this sets __hash__ = object.__hash__ on RunningCommand.

Changes

• Added __hash__ = object.__hash__ to RunningCommand in src/sh/__init__.py.
• Added regression test test_async_gather in tests/sh_test.py verifying hashability, set/dict lookups, and concurrent completion with asyncio.gather.

Closes #800