fix(fs-node): close the original descriptor after stream release

[xianjianlf2]

When FileHandle.close() waits for an active Web Stream reference, cancelling that stream runs unref(). The method sets fd = -1 before passing the descriptor to fs.close(), so the pending close rejects with EBADF and the original descriptor remains open. Capture the original descriptor before marking the handle closed, as the immediate close path already does.

Regression tests cover cancellation both before and after a stream read, shared concurrent close calls, and an assertion that the original descriptor is actually closed. Both new cases fail with EBADF before the fix.

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