Windows packaging: Scoop manifest + winget

[stefanthearchitect]

Context

GoReleaser already cross-compiles Windows archives to dl.turborg.com, and there's an install.ps1. Scoop and winget are the idiomatic Windows package managers and would widen reach.

The task

• Add a Scoop manifest (GoReleaser has scoops: support) pointing at the released zip.
• Add a winget manifest / submission flow.

Either one is a useful PR on its own.

Acceptance

• scoop install turborg (from the bucket) installs a working binary at the released version.
• winget manifest validates and installs.
• Documented in the README's install section.