Automate Env mirror selection and Python venv activation

[Copilot]

Installation no longer requires users to select a regional command. Linux and Windows detect the network region, clone from the suitable mirror, then restore repository remotes to GitHub.

• Automatic mirror selection

  • Detect China-based IPs via ipinfo.io.
  • Use regional mirrors for installer dependencies and Env repository clones.
  • Reset cloned packages, sdk, and env remotes to GitHub.

• Virtual environments

  • env.sh now creates and activates ~/.env/.venv on first use.
  • Installs Env dependencies inside the venv.
  • Cleans up incomplete venvs and reports setup failures.
  • Adds python3-venv to Ubuntu and SUSE prerequisites.

source ~/.env/env.sh
# Creates and activates ~/.env/.venv on first use

• Windows setup

  • Applies automatic mirror detection to Git, pip, and Env bootstrap downloads.
  • Corrects the existing .env replacement prompt behavior.

• Documentation

  • Removes region-specific installation commands and obsolete mirror troubleshooting.
  • Documents automatic mirror selection and first-use venv activation.