refactor: reorganize configure-env.sh with logical prompt ordering and gating

Prompts now flow in logical order: Cluster Connection → Installation Mode →
Operators → Runtime. Irrelevant questions are hidden based on earlier answers
(e.g. skip-all hides all operator questions, skip-COO hides COO images,
catalog-install hides bundle image prompts). Kubeconfig defaults to
~/.kube/config so oc login is sufficient. Extracted pick_kubeconfig_interactive
to deduplicate ~120 lines of Downloads scanning logic.

configure-env.sh fixes:
- Fix `[[ ]] && assignment` patterns that crash under set -euo pipefail
  when the test is false (exit code 1 triggers set -e)
- Add zsh compatibility: when sourced from zsh, delegates interactive
  prompts to bash then auto-sources the generated export-env.sh
- Add prominent message in non-sourced mode about needing to source

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: DavidRajnoha