Document Windows/PowerShell equivalents for QUICKSTART

[cobusgreyling]

Summary

Add Windows/PowerShell command equivalents alongside bash examples in QUICKSTART.md (and linked docs where duplicated).

Acceptance criteria

• QUICKSTART.md has a Windows/PowerShell section or inline equivalents
• Covers: clone, install, build, demo, npx @cobusgreyling/outerloop init, evidence/verdict/ledger commands
• Notes pnpm/npm prerequisites on Windows
• Links from README or QUICKSTART intro

References

• QUICKSTART.md