chore: prepare h3x v0.6.0-beta.4

[eareimu]

Summary

• bump h3x to 0.6.0-beta.4
• advance the direct dquic requirement to the same-wave 0.7.0-beta.4 release
• preserve the explicit tested transport dependency graph for downstream releases

Release

• Surface: crates.io (h3x), incremental prerelease
• Planned tag: v0.6.0-beta.4
• Dependency gate: dquic 0.7.0-beta.4 is visible on crates.io
• Downstream: publish dshell only after this version is registry-visible

Verification

• cargo +nightly fmt --check
• cargo +stable clippy --all-targets --all-features -- -D warnings
• cargo +stable test --all-features --all-targets
• cargo +stable semver-checks --baseline-version 0.6.0-beta.3 --release-type patch --default-features
• cargo +stable publish --dry-run

cargo-semver-checks uses default features because its all-feature rustdoc build cannot provide the downstream-selected remoc RPC codec; the repository's all-feature clippy and test gates passed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
see 6 files with indirect coverage changes

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• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[eareimu]

暂停本发布 PR：dquic 在 v0.7.0-beta.3 后发现并修复了路径可接纳性问题。待新的 dquic 版本发布并在 crates.io 可见后，再更新 h3x 的版本与直接依赖约束。