Create repositories from GitHub templates

[cursor]

Summary

Allow creating repositories from a GitHub template repository.

Motivation

Listed in docs/cli.md Related APIs. Common workflow beyond empty/auto_init create.

Proposed CLI

github-rest-cli repo create -n NAME [-o ORG] --template OWNER/REPO \
  [--include-all-branches] [--public|--private|--internal]

Constraints: --template and --empty are mutually exclusive.

Implementation notes

• Endpoint: POST /repos/{template_owner}/{template_repo}/generate
• Branch in create_repository (or helper) when template is set
• parser flags + validation
• tests, docs/cli.md, CHANGELOG

Acceptance

• Creates from user/org template into user or org destination
• Rejects --empty with --template
• Docs + tests updated