Feature: Support Installation via winget (Windows)

[GordonBeeming]

Description
For a "first-class" Windows experience, we should add copilot_here to the Windows Package Manager (winget) manifest. This complements the December work of hardening the tool for PowerShell 5.1 and Core.

Acceptance Criteria

• Submit a manifest to the microsoft/winget-pkgs repository.
• Support winget install copilot_here.
• Ensure the installer handles the placement of the native binary and any required environment variables.