fix: apply all FIX-TODO items (P0/P1/P2)

P0 bugs:
- Invoke-CIJob.ps1: skip --depth 1 when $Commit specified (shallow clone
  + checkout specific commit was silently failing)
- Get-BuildArtifacts.ps1: check .Length -eq 0 not rounded sizeKB (false
  fail on artifacts smaller than 50 bytes)
- build-nsis.yml: upgrade upload-artifact v3 -> v4 (v3 deprecated)

P0 security:
- Remove hardcoded default password CIBuild!ChangeMe2026 from all scripts,
  README, TODO; prompt Read-Host -AsSecureString at runtime instead
- Setup-TemplateVM.ps1: replace `net user $u $p /add` (password in argv /
  audit log 4688) with New-LocalUser + local ConvertTo-SecureString
- Prepare-TemplateSetup.ps1: save and restore WSMan AllowUnencrypted +
  TrustedHosts in finally block (was permanently mutating host WinRM config)
- Setup-TemplateVM.ps1: remove duplicate MaxMemoryPerShellMB (winrm set
  + Set-Item both setting same value)

P1 doc (stale Host-Only / VMnet11 era):
- Setup-TemplateVM.ps1: rewrite NETWORK REQUIREMENT block + final steps
  (system uses VMnet8 NAT permanently, not VMnet11 Host-Only)
- Invoke-CIJob.ps1 Phase 1 comment: correct network model
- ARCHITECTURE.md: remove Git from toolchain list (not installed); clarify
  zip-transfer rationale (no PAT in VM, not network isolation)
- BEST-PRACTICES.md: rewrite Step 8 as NAT topology verification

P1 minor:
- Invoke-RemoteBuild.ps1: remove wasted first New-Item (created then
  immediately removed and recreated)
- Wait-VMReady.ps1: remove unused $elapsed; simplify try/catch around
  native command (exit codes don't throw)
- Install-Runner.ps1: add deprecation notice pointing to Setup-Host.ps1

P2 operational:
- Add scripts/Cleanup-OrphanedBuildVMs.ps1 with -WhatIf support
- Get-BuildArtifacts.ps1 -IncludeLogs: add -Recurse (msbuild logs in subdir)
- Add gitea/workflows/lint.yml (PSScriptAnalyzer on .ps1 push/PR)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/Get-BuildArtifacts.ps1

@@ -93,7 +93,7 @@ try {
     # ── Copy logs if requested ────────────────────────────────────────────
     if ($IncludeLogs) {
         $logFiles = Invoke-Command -Session $session -ScriptBlock {
-            Get-ChildItem -Path 'C:\CI\build' -Filter '*.log' -ErrorAction SilentlyContinue |
+            Get-ChildItem -Path 'C:\CI\build' -Filter '*.log' -Recurse -ErrorAction SilentlyContinue |
                 Select-Object -ExpandProperty FullName
         }
 
@@ -109,10 +109,11 @@ try {
         throw "Artifact was not found at expected host path after copy: $hostDestPath"
     }
 
-    $sizeKB = [math]::Round((Get-Item $hostDestPath).Length / 1KB, 1)
-    if ($sizeKB -eq 0) {
+    $fileItem = Get-Item $hostDestPath
+    if ($fileItem.Length -eq 0) {
         throw "Artifact file exists but is empty: $hostDestPath"
     }
+    $sizeKB = [math]::Round($fileItem.Length / 1KB, 1)
 
     Write-Host "[Get-BuildArtifacts] Artifact collected: $hostDestPath ($sizeKB KB)"
     return $hostDestPath