fix(parser): accept mismatched terminal codes

[veeso]

Description

Restores the intent of #168 by accepting non-standard multiline FTP replies whose terminal line uses a different three-digit status code. The parser now returns that terminal status in the sync, Tokio, and smol backends while preserving the existing FEAT flow, where the 211- opener must be returned before feature lines are read. This supports servers such as glFTPd without regressing FEAT parsing.

Adds deterministic regression tests for mismatched terminal codes and FEAT parsing across all three backends.

Related to #168.

Checklist

• I have read the AI Policy and the contributing guidelines.
• I have added rustdoc documentation for any new public API.
• I have added tests covering my changes.
• just check_code passes locally.
• My commits follow the Conventional Commits format (the CHANGELOG.md is generated from them at release time).

AI Disclosure

OpenAI Codex was used to inspect PR #168, reason about the FEAT regression, implement and test the fix, and prepare this commit and PR. I reviewed the diff and test results and take responsibility for the contribution.

[cocogitto-bot]

✔️ e2b4d97 - Conventional commits check succeeded.

[veeso]

Thanks for #168 @elirancv, it was mostly correct, just not covering the FEAT command case. Sorry for the late response; it's been on my to-do list for a couple of weeks, but I was planning to work on it soon.