[fix]: 修复通过curl命令安装场下下ubuntu/debian等系统触发系统保护无法安装的openviking的问题

[LinQiang391]

Description

• install.sh: PEP 668 and no-pip detection; venv (ensurepip / venv --without-pip + get-pip.py / virtualenv); reuse existing venv; plugin download retry and progress; OPENVIKING_ALLOW_BREAK_SYSTEM_PACKAGES opt-in; configPath as OPENVIKING_DIR/ov.conf (absolute)
• install.ps1: configPath absolute (Join-Path OpenVikingDir ov.conf)
• setup-helper/cli.js: configPath absolute (join OPENVIKING_DIR ov.conf)
• INSTALL*.md: FAQ for externally-managed-environment and venv/pipx

Related Issue

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)
• Performance improvement
• Test update

Changes Made

Testing

• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have tested this on the following platforms:
  • Linux
  • macOS
  • Windows

Checklist

• My code follows the project's coding style
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)

Additional Notes

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