Fix unix socket half-close handling in Sockets

[abslock128w]

Summary

Fix incorrect handling of unix domain socket half-close where a
PipeEndpoint was fully closed on UV_EOF, even when the write side
was still usable.

Problem

When libuv reports UV_EOF, Julia currently finalizes certain
LibuvStreams (notably PipeEndpoint) too aggressively.
This breaks valid half-close semantics, where the read side reaches EOF but the socket remains writable.
This behavior causes issues in clients that rely on
half-closed unix sockets, forcing workarounds such as splitting stdio
into multiple sockets.

Solution

Update uv_readcb to preserve the stream when the underlying handle
remains writable, allowing correct half-close behavior while still
closing truly unusable streams.

The change aligns Julia’s behavior with libuv semantics and POSIX
expectations.

[tecosaur]

Ref: #60959

@abslock128w apologies if this is unfounded, but I get the sense that LLMs may have been used in formulating this PR. If this is the case, we would appreciate it if you would declare this.

[abslock128w]

Ref: #60959

@abslock128w apologies if this is unfounded, but I get the sense that LLMs may have been used in formulating this PR. If this is the case, we would appreciate it if you would declare this.

yeah I did use an LLM a bit while working on this, used it to understand the already writtne code
but the actual debugging, writing the test, and running the tests was done by me.
english isntt really my first language and its not that good...
so i usually use llm to translate what i want to say

[fingolfin]

Enabling "Hide whitespace" in the GitHub diff viewer, it seems to me that the changes to this function amount to:

1. wrapping most of the code into a try/finally/end with unlock in the finalize block -- that seems plausible;
2. inserting some empty lines, wrapping an overly long line -- I am neutral on this;
3. removing or reducing a lot of comments -- that part seems less plausible: why do we want to remove comments or reduce them? Were they incorrect?

[abslock128w]

Hey there,
Thank you for pointing out the mistake!
I am new to this whole open source contribution thing...
And about the comment part I never really use comments that's wrong on my part ( i know its a good practice to do so,
will try to keep that in mind as I move forward! )

[fingolfin]

Why is reseteof(x::TTY) being removed?

[abslock128w]

I mistakenly removed the TTY fucntion
This will probably brake the interactive input...
Will add in the next commit.
Again thank you for pointing it out!