Add package manager support for WinGet, Chocolatey, Scoop

[DRSDavidSoft]

Tip

Status: On hold until after the development merge into master; this PR keeps registry ownership and submission steps manual while preparing repeatable release assets for the community and core maintainers.

Summary

Refs #3094.

• add scripts/package-managers.ps1 to generate WinGet manifests and Chocolatey package sources from official Cmder release assets and hashes.txt
• add Scoop manifest generation for the existing cmder and cmder-full package paths
• add docs/package-managers.md with the release-time flow for WinGet, Chocolatey, and Scoop
• add a dry-run-first package-manager publishing workflow for WinGet, Chocolatey, and Scoop
• keep external publishing gated behind explicit maintainer secrets, variables, and workflow inputs until ownership, policy, and credentials are settled

Validation

• generated package-manager output from a Cmder release asset set with scripts/package-managers.ps1
• parsed generated Scoop manifests as JSON
• validated generated WinGet manifests with winget validate
• built generated Chocolatey packages with choco pack

Chocolatey reported only the local machine's pending reboot warning during choco pack; package creation succeeded for both generated packages.