Fix apt_conffile_report exiting 1 when uutils comm sees locale-sorted input

[BadFlo]

✍️ Description

On Ubuntu 26.04 (uutils coreutils), apt_conffile_report() makes every update end with exit code 1 when a container has two or more leftover *.dpkg-new / *.dpkg-dist files. _cs_conffile_list sorts with the locale, uutils comm compares bytes, so comm declares its input unsorted and exits 1. The ERR trap then reports a failure even though the update worked.

Fix: sort and compare in the same order.

• _cs_conffile_list: sort -> LC_ALL=C sort
• apt_conffile_report: comm -13 -> LC_ALL=C comm -13

Details and reproduction (with a verbose log) are in the linked issue, which I filed in ProxmoxVE because I hit it through ct/plex.sh.

🔗 Related Issue

Fixes community-scripts/ProxmoxVE#17967

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – The real functions were run on an Ubuntu 26.04 LXC on Proxmox VE with three leftovers that sort differently by locale and by byte. Unpatched: ERR trap rc=1. Patched: rc=0 and the new conffile is still reported. Not tested on Incus (the change is plain shell and not backend-specific).
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.
• API.txt regenerated – Not applicable, no function signature or behavior change.

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🤖 AI Assistance (X in brackets)

• No AI used – Code was written without AI assistance.
• AI was used – Claude (Sonnet 5.5) found the cause and wrote the two-line change. I reviewed it and ran the test on my own container, and I take responsibility for it matching this repo's conventions.

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🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing behavior in a way that may require updates in every downstream script.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, docs/, CONTRIBUTING.md, or other docs.

🤖 Generated with Claude Code

[github-actions]

Try this branch

The engine and the scripts resolve independently, so a production script can
be run against the engine from this PR by setting one variable:

COMMUNITY_SCRIPTS_CORE_URL=https://raw.githubusercontent.com/BadFlo/core/fix-conffile-report-comm-order \
bash -c "$(curl -fsSL https://raw.githubusercontent.com/community-scripts/ProxmoxVE/main/ct/debian.sh)"

Swap ct/debian.sh for whatever exercises the change.

Run a script from a fork as well

curl -fsSL https://raw.githubusercontent.com/BadFlo/core/fix-conffile-report-comm-order/tools/run.sh |
  bash -s -- https://raw.githubusercontent.com/YOU/DevScripts/your-branch ct/debian.sh \
             https://raw.githubusercontent.com/BadFlo/core/fix-conffile-report-comm-order

Note that run.sh is reached through a pipe, so the script it starts inherits
an exhausted stdin. Whiptail is fine — it opens /dev/tty — but a plain read
would see EOF. The single-variable form above does not have that problem.

Useful flags while testing

dev_mode=net logs every engine fetch with status and duration, which is the
quickest way to confirm the branch is really being used. dev_mode=keep stops a
failed build from deleting the container along with the evidence.