feat(vscode): add one-click Compass CLI onboarding

[forhappy]

Summary

• add one-click Compass CLI installation from a visible VS Code terminal on macOS, Linux, and Windows
• add and publish an official PowerShell installer with checksum verification and Windows CI coverage
• automatically discover, verify, and activate the installed CLI without reloading VS Code
• present a clear “Compass is ready” state with one primary “Initialize repository” action
• add bounded retry, timeout, terminal-close, incompatible-version, and existing-CLI recovery paths

Why

New extension users currently reach a dead end when Compass is not installed. This flow keeps the official install command visible, lets users install in one action, and immediately advances them to repository initialization after verification.

Validation

• JavaScript/TypeScript type checks passed
• 162 viewer and extension unit tests passed
• 64 Playwright tests passed
• VS Code extension-host integration passed
• VSIX packaging and smoke verification passed
• deterministic viewer asset verification passed
• shell installer release tests passed
• PowerShell installer testing is wired into Windows CI; PowerShell was unavailable in the local macOS environment

No graphify update . was run, per request.