Fix curl error handling and revert maintainer to project address

[Copilot]

Summary

• Purpose and scope - Addresses code review feedback on PR Feat/easy install #4
• Linked issue
• Testing done - Shellcheck passed, curl error handling verified

Changes

Error handling:

• Added -f flag to curl in libexec/kctl-env-list-remote so HTTP errors (403 rate limit, 404, 5xx) trigger the error handler instead of silently failing with empty output

Maintainer metadata:

• Reverted personal email to project address (kctl-env Maintainers <kctl-env@example.com>) in:
  • packaging/debian/control Maintainer field
  • scripts/release.sh Debian changelog entry
  • scripts/release.sh RPM changelog entry

Checklist

• Branch based on latest main
• No direct commits to main
• Updated README.md / docs if needed
• Updated CHANGELOG.md for user-facing changes
• Added/updated tests (if applicable)
• For releases: used make release V=X.Y.Z and opened PR from release/vX.Y.Z

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[Copilot]

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com/repos/kubernetes/kubernetes/tags
  • Triggering command: /usr/bin/curl curl -sSLf REDACTED (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)