fix: PS7 double-install, false hostname failure; WinUtil Standard preset

[Stensel8]

Summary

• Start.ps1: poll up to 20s (and log winget's exit code) after installing PowerShell 7 via WinGet instead of a single check 5s later, so a slow-to-register install isn't mistaken for a failure that then also triggers the MSI fallback, installing PowerShell 7 twice.
• Set-HostName.ps1: exit 0 (not 1) when no valid BIOS serial number is found. That's an expected, already-handled case (common on VMs), not a failure - it was making Deploy.ps1 report "Some deployment steps failed" on otherwise-clean runs.
• Deploy.ps1 / Apply-Tweaks.ps1: -Tweaks now defaults to Yes (including under -NonInteractive), so the WinUtil Standard preset just runs instead of requiring an explicit opt-in. -Tweaks No still skips it.
• README: drop the "Option 3" windeploy.stensel.nl one-liner - it pointed at the pre-migration repo and isn't part of this one.
• Docs and changelog updated to match.

Type of change

• feat — new feature or script
• fix — bug fix

PR title and commit types must follow these standards — view the contributing guide

Checklist

• PR title follows the commit convention
• Tested on a real Windows 11 25H2 machine (required for anything under Scripts/ or Docs/ — CI cannot exercise BitLocker, Sysprep, WinGet or Defender)
• PSScriptAnalyzer passes locally
• No hardcoded IPs, credentials, or company-specific data
• Both EN (*.md) and NL (*.nl.md) versions updated, if src/content/ changed
• No broken internal links, if src/ changed
• Site tested locally with cd src && hugo server, if src/ changed

Notes

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