feat(io,tls)!: require Splittable for AsyncStream

[Berrysoft]

Previously we require for<'a> &'a S: AsyncRead + AsyncWrite to ensure that the inner stream is OK to be called read and write simultaneously, but it is not perfect. A user can still construct unsound code with it. Now we require Splittable directly for safety.

A new type CompatMaybeTlsStreamInner is also added to loose the type requirements. After this PR, I think I'll rewrite compio-ws to use it and make the websocket stream splittable directly without another compat type.

[Copilot]

Pull request overview

This PR tightens I/O safety guarantees across TLS and WebSocket integration by requiring Splittable for streams that may be read and written concurrently (notably through compat::AsyncStream and TLS stream wrappers), and introduces a futures-util compatibility wrapper for MaybeTlsStream.

Changes:

• Require util::Splittable (plus ReadHalf/WriteHalf bounds) for compio_io::compat::AsyncStream and for TLS/WebSocket stream generics that rely on concurrent read/write.
• Update compio-tls stream types (TlsStream, MaybeTlsStream, rustls acceptor types) to use Splittable-based bounds instead of for<'a> &'a S: AsyncRead + AsyncWrite.
• Add CompatMaybeTlsStream and MaybeTlsStream::into_compat() to provide futures_util::AsyncRead/AsyncWrite compatibility.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
compio-ws/src/tls.rs	Updates WebSocket TLS helpers to require Splittable and half bounds for safe duplex usage.
compio-tls/src/stream.rs	Makes TlsStream require Splittable and expresses read/write capability via halves.
compio-tls/src/rtls.rs	Applies Splittable + half bounds to rustls lazy acceptor/handshake wrapper types.
compio-tls/src/maybe.rs	Makes MaybeTlsStream Splittable-based and adds CompatMaybeTlsStream + into_compat().
compio-tls/src/adapter.rs	Updates TLS connector/acceptor APIs to require Splittable and half bounds.
compio-tls/Cargo.toml	Makes futures-util non-optional to match unconditional usage.
compio-io/src/compat/async_stream.rs	Reworks AsyncStream to require Splittable and internally split into read/write halves.

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 6 comments.

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[George-Miao]

LGTM