Read config files as UTF-8 and keep durable profile backups

[26zl]

Draft: install/uninstall paths are Windows-specific and can't be fully exercised here (no winget/elevation/ssh.exe), so the runtime effect is verified by reasoning + parse/analyzer only.

Fix B1 - UTF-8 reads (setup.ps1)

On Windows PowerShell 5.1 a bare Get-Content -Raw decodes with the system ANSI code page, so non-ASCII (e.g. the Norwegian letters) in settings got corrupted and then written back. Added -Encoding UTF8 to the Get-Content -Raw reads of:

• user-settings.json (Save-WizardChoices + merge step)
• Windows Terminal settings.json (the read-back before rewrite)
• theme.json / terminal-config.json bundle temp files
• the downloaded Oh My Posh theme (validation read)
• the wizard state file

Writes already use [IO.File]::WriteAllText(..., UTF8Encoding(false)) (no BOM), so only reads needed fixing. No Set-Content -Encoding UTF8 introduced (that would BOM on PS5.1 and trip CI).

Fix B2 - durable backups

• setup.ps1: on first install, save a one-time profile.original.ps1. The existing oldprofile*.ps1 rotation (keep 5) never matches that name, so the user's pre-install profile is no longer lost after 5 installs.
• Uninstall-Profile: if profile.original.ps1 exists, restore it over the profile (and drop the marker) instead of just deleting; otherwise the previous remove behavior is unchanged (so the -WhatIf "Remove profile file" path is preserved).
• Update-Profile: back up the current profile to a rotated oldprofile.<stamp>.ps1 (keep 5) before overwriting it.
• sed helper: read via the repo's Get-Utf8FileText (BOM-aware UTF-8) and write a single .bak of the pre-edit content before rewriting.

Fix C - README (install-wizard section)

The "Install Wizard" section recommended -SkipHashCheck as the "Default trusted-download flow". Reworded it to match the already-review-first Quick Install block at the top: run with no hash flag (prints hashes, stops), then re-run with -ExpectedSha256; -SkipHashCheck is labelled the unverified fallback. Added a one-line note that a signed-release / tag-pinning model is a maintainer follow-up (did not redesign the release model).

Verification

• Parser::ParseFile clean on setup.ps1 and the profile.
• PSScriptAnalyzer (CI exclude set) on both: 0 findings.
• No non-ASCII and no Set-Content -Encoding UTF8 in the changed .ps1 files.
• Unverified here: the actual install/uninstall/update file operations (need Windows + elevation); the sed .bak behavior is reasoned, not run. No workflows touched.

Follow-ups for the owner

• The existing tests/test.ps1 uninstall sandboxes don't create profile.original.ps1, so they still exercise the plain-remove path; a case covering original-restore would be worth adding.
• The profile already reads most settings via Get-Utf8FileText; a sweep for any remaining bare Get-Content -Raw | ConvertFrom-Json there could be a small follow-up.