Preserve DNS resolver order in diagnostics and HTTP/3

[ryanfowler]

Summary

• Keep transport socket addresses in resolver order so diagnostics no longer change connection preference.
• Switch DNS timing output to stable deduping in original resolver order instead of sorting by family.
• Reuse the first resolved address family for HTTP/3 preference/fallback, matching TCP connect_first.
• Remove the unused sorted IP helper and update the repo guidance to match the new invariant.

Testing

• cargo fmt
• cargo clippy --locked --all-targets --all-features -- -D warnings
• cargo test --all-features
• cargo test --all-features --test cli --test formatting --test grpc --test http --test network --test terminal --test update --test websocket -- --test-threads=1