refactor(version): validate existence of version for PS script

The PowerShell script should validate that the tag doesn't already exist before attempting to create it. Add: if (git rev-parse \"v$NewVersion\" 2>$null) { Write-Error \"Tag v$NewVersion already exists\"; exit 1 } before line 12.

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: ArchILLtect

scripts/release-bump.ps1

@@ -13,6 +13,7 @@ if (Select-String -Path CHANGELOG.md -Pattern '\[Unreleased\]:') {
 }
 & git add pom.xml CHANGELOG.md
 & git commit -m "chore(release): v$NewVersion"
+if (git rev-parse "v$NewVersion" 2>$null) { Write-Error "Tag v$NewVersion already exists"; exit 1 }
 & git tag -a "v$NewVersion" -m "Release v$NewVersion"
 Write-Output "Version bumped to $NewVersion. Next: push branch + tag."