[Donotavio]

Problem

`rtk docker ps` fetches `{{.Status}}` which already includes health state when configured:
```
Up 2 hours (healthy)
Up 1 hour (unhealthy)
```

But `docker_ps()` parsed `parts[2]` (Status field) and discarded it completely. An AI agent monitoring containers had no way to identify unhealthy services.

Fix

• Include Status field in output between name and image
• Prefix unhealthy containers with `[!]` for immediate visibility
• All other states (healthy, plain Up, Exited, Restarting) pass through verbatim

Refactoring

• Extract `format_docker_ps_line(parts) -> Option` as `pub(crate)` pure function — directly unit-testable without spawning docker
• Extract `trim_image_registry()` helper — eliminates duplication with `format_compose_ps()` which had the identical `.split('/').next_back()` pattern
• Add `UNHEALTHY_PREFIX` constant

Tests

7 new unit tests:

• `test_docker_ps_preserves_healthy_status` — (healthy) shown verbatim, no [!]
• `test_docker_ps_marks_unhealthy_prominently` — [!] prefix present
• `test_docker_ps_shows_status_without_health_check` — plain Up shown
• `test_docker_ps_exited_no_flag` — Exited shown, no [!]
• `test_docker_ps_restarting_no_flag` — Restarting shown, no [!]
• `test_docker_ps_line_too_few_parts_returns_none` — None guard for malformed input
• `test_docker_ps_formats_all_five_containers` — all 5 states in one pass

---

Identified via adversarial testing: https://www.reddit.com/r/ClaudeCode/comments/1spiy8t/

[CLAassistant]

All committers have signed the CLA.

[rtk-release-bot]

This pull request has been automatically marked as stale due to 90 days of inactivity. If this pull request is still relevant, please leave any comment (for example, "bump"), and we'll keep it open. Your contribution is very much appreciated — we're sorry we haven't been able to review it yet.

[KuSh]

Thanks for this. The docker ps line formatting was pulled into its own helper on develop as format_container_line_from_parts, shared with docker ps -a, and it now prints the container status, first in #1895 on 2026-05-19 and then in commits 861a46d, 3d4189c and b52db52 in June, which also added the never-worse guard and the tee hint around it. Because develop prints the fields in a different order (id, name, image, status), the tests here assert a shape that no longer exists. Two things from this PR are still missing on develop: there is no visual marker such as [!] when a health check is failing, so (unhealthy) reads like any other status text, and the registry trim is still duplicated at three call sites instead of a shared helper. Both would be welcome as a small issue or a narrow PR on the current helper. If I missed a part of this, please comment or reopen.