feat(cli): uninstall opencode installed via windows package managers

[itsrainingmani]

Fixes: #8573

What does this PR do?

• Adds uninstall information and commands for choco/scoop installs
• Extends bun remove -g opencode-ai on windows to clean leftover installed artifacts -
  • binaries: .bun\bin\opencode.{exe|bunx}
  • node_modules: .bun\install\global\node_modules\opencode-windows-x64{-baseline}
• Informs user if they're trying to uninstall opencode via choco from a non-elevated command shell

How did you verify your code works?

I tested every install method on Windows (Windows Terminal, WezTerm) and uninstalled w/ every method to ensure that the uninstallation happens cleanly and does not leave behind artifacts.

Bun Remove

Choco Uninstall

Scoop Uninstall