fix(wasix): preserve nonblocking connect errors

[kilyanni]

Preserve the underlying error when a nonblocking socket connection fails.

[Copilot]

🟡 Changes recommended

It introduces new variants to the public virtual-net::NetworkError enum (a breaking API surface change) without corresponding versioning/release-note handling.

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Pull request overview

This PR improves nonblocking socket connect error reporting in WASIX by preserving and surfacing the underlying connect failure (e.g., ECONNREFUSED, ENETUNREACH, EHOSTUNREACH) instead of collapsing failures to ENOTCONN.

Changes:

• Extend virtual networking errors with NetworkUnreachable and HostUnreachable, including IO error kind and OS error code mappings.
• Map the new virtual-net errors to WASIX Errno values (Netunreach, Hostunreach).
• Update sock_connect’s nonblocking path to read and return the socket’s latched last error on Closed/Failed, falling back to ENOTCONN when none is recorded.

File summaries

File	Description
lib/wasix/src/syscalls/wasix/sock_connect.rs	Uses the socket’s latched last_error() to return the real connect failure for nonblocking connects.
lib/wasix/src/net/mod.rs	Maps new NetworkError variants to WASIX Errno values.
lib/virtual-net/src/lib.rs	Introduces NetworkUnreachable/HostUnreachable and maps them to/from std::io::ErrorKind and relevant libc codes.

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 1
• Review effort level: Lite

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[kilyanni]

... oh. Right. Well that's fun ^^'

[Arshia001]

virtual-net is not stable yet and breaking changes aren't unexpected. Indeed, with each release, we bump the minor.

[Arshia001]

Looks good to go as soon as we add tests for it in wasm_tests.