release: prepare h3x v0.4.1

[eareimu]

Summary

Prepare the incremental h3x 0.4.1 release.

Changes included:

• retain fix(dquic): avoid retaining endpoint companion connections
• bump the crate version from 0.4.0 to 0.4.1
• exclude fix(dquic): guard pending sni handshakes from this release branch

Release metadata

• Repository: h3x
• Target branch: main
• Release surface: crates.io package h3x
• Initial vs incremental: incremental release
• Planned tag: v0.4.1
• Dependency state: final manifest uses published crates.io dependencies; no git = ... dependencies in Cargo.toml

Validation

Previous local checks before the branch correction:

• cargo +nightly fmt --check
• cargo publish --dry-run
• rg -n "git\\s*=" Cargo.toml returned no matches

After the branch correction:

• branch history was rewritten to main + fix(dquic): avoid retaining endpoint companion connections + release: prepare v0.4.1
• fix(dquic): guard pending sni handshakes is no longer in the PR history

Local caveat:

• Full local cargo test --all-features --all-targets is not reliable on this macOS host because several dquic network tests assume Linux lo; this host exposes lo0.

GitHub CI on Linux is the release gate for this PR.