fix: ponytail audit — remove ~330 lines of redundant code (#30)

- lib: add err(), --api-version param to gh_api()
- close-archived-alerts: collapse 3 close_*_alerts() into 1 generic
  close_alerts(); replace hand-rolled pagination with gh_api_paginate
- copilot-report: collapse _copilot_api() 30→3 lines using --api-version;
  remove info()/warn() pass-through aliases
- repo-permissions-report: remove info() pass-through alias
- dockerfile-discovery: delete dead gh_api_link() + RESPONSE_LINK global;
  remove vestigial print_* redefines; inline check_prerequisites()
- get-public-repos: inline check_prerequisites(); drop no-op print_error override
- 7 pagination scripts: remove local get_repo_pagination() wrappers, use
  lib get_repo_page_count() directly
- organize-stars: replace 7-line command check loop with require_command
- archive-old-repos: inline validate_environment(); move local declarations
  to assignment site; drop stale comments
- auto-repo-creation: merge add_teams_to_repo + add_repo_owners_to_repo
  into single add_team_to_repo with permission param
- docs: update AGENTS.md and copilot-instructions.md with err(), --api-version,
  correct pagination example, and fill blank shared-library section

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: locus313