fix(buf,driver): safety around set_len

[Berrysoft]

Closes #581
Closes #582

[Copilot]

Pull request overview

This PR adds explicit safety requirements to buffer length manipulation methods by making map_advanced and map_vec_advanced unsafe functions. This ensures callers are aware that these methods call set_len internally, which has safety requirements about the validity of the new length.

Key changes:

• Made BufResultExt::map_advanced and VecBufResultExt::map_vec_advanced trait methods unsafe
• Updated all call sites to wrap these method calls in unsafe blocks
• Removed begin_or_cap() method in Slice<T> and replaced its usage with begin_or_len()

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
compio-driver/src/op.rs	Added unsafe to trait method signatures for map_advanced and map_vec_advanced, with safety documentation explaining the requirements
compio-buf/src/slice.rs	Removed begin_or_cap() helper method and changed range() to use begin_or_len() instead
compio-process/src/windows.rs	Updated ChildStdout and ChildStderr read implementations to call map_advanced() in unsafe blocks
compio-process/src/unix.rs	Updated ChildStdout and ChildStderr read implementations to call map_advanced() in unsafe blocks
compio-net/src/socket.rs	Updated multiple socket receive methods to call map_advanced() and map_vec_advanced() in unsafe blocks
compio-fs/src/stdio/windows.rs	Updated Stdin read implementation to call map_advanced() in an unsafe block
compio-fs/src/pipe.rs	Updated Receiver read implementations to call map_advanced() and map_vec_advanced() in unsafe blocks
compio-fs/src/file.rs	Updated File read implementations to call map_advanced() and map_vec_advanced() in unsafe blocks
compio-fs/src/async_fd.rs	Updated AsyncFd read implementations to call map_advanced() and map_vec_advanced() in unsafe blocks

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[Berrysoft]

Clippy suggests that we should not use as_slice as the method name. @George-Miao I suggest as_init.

[George-Miao]

@Berrysoft Sure. Sounds good to me.

[Berrysoft]

It's a bit massive to change the names. I chose another way to fix the CI.

[Berrysoft]

Ping @George-Miao

[George-Miao]

LGTM