feat: stream build output in real-time + log capture and retention

Invoke-RemoteBuild.ps1:
- Custom build command: replace buffered collect-then-print with
  Write-Host streaming inside Invoke-Command (WinRM forwards Write-Host
  in real-time to the host console)
- Set PYTHONUNBUFFERED=1 in the remote session to prevent Python from
  holding lines in its internal buffer
- Same streaming approach for dotnet restore and dotnet build paths
- Return value is now just int exit code instead of hashtable

Invoke-CIJob.ps1:
- Add -LogDir parameter (default F:\CI\Logs)
- Add -LogRetentionDays parameter (default 30)
- Start-Transcript at job start -> F:\CI\Logs\<JobId>\invoke-ci.log
- Stop-Transcript in finally block (guaranteed execution)
- Auto-purge log directories older than LogRetentionDays after each job

scripts/Invoke-RemoteBuild.ps1

@@ -132,13 +132,16 @@ try {
     if ($BuildCommand -ne '') {
         # ── Custom build command (e.g. python, msbuild, cmake…) ──────────
         Write-Host "[Invoke-RemoteBuild] Running build command: $BuildCommand"
-        $buildResult = Invoke-Command -Session $session -ScriptBlock {
+        $buildExit = Invoke-Command -Session $session -ScriptBlock {
             param($workDir, $cmd, $artifactZip, $artifactSrc)
+            # Unbuffered Python output — lines appear in real-time instead of being held in buffer
+            $env:PYTHONUNBUFFERED = '1'
             Set-Location $workDir
-            $output = Invoke-Expression "$cmd 2>&1" | ForEach-Object { "$_" }
-            $buildExit = $LASTEXITCODE
+            # Stream each output line via Write-Host — WinRM forwards Write-Host in real-time
+            & cmd /c "$cmd 2>&1" | ForEach-Object { Write-Host $_ }
+            $exit = $LASTEXITCODE
 
-            if ($buildExit -eq 0) {
+            if ($exit -eq 0) {
                 $archiveDir = Split-Path $artifactZip -Parent
                 if (-not (Test-Path $archiveDir)) {
                     New-Item -ItemType Directory -Path $archiveDir -Force | Out-Null
@@ -147,38 +150,36 @@ try {
                 Compress-Archive -Path $srcPath -DestinationPath $artifactZip -Force
             }
 
-            return @{ ExitCode = $buildExit; Output = ($output -join "`n") }
+            return $exit
         } -ArgumentList $GuestWorkDir, $BuildCommand, $GuestArtifactZip, $GuestArtifactSource
 
-        Write-Host $buildResult.Output
-        if ($buildResult.ExitCode -ne 0) {
-            throw "Build command failed (exit $($buildResult.ExitCode))"
+        if ($buildExit -ne 0) {
+            throw "Build command failed (exit $buildExit)"
         }
     }
     else {
         # ── Default: dotnet restore + dotnet build ────────────────────────
         Write-Host "[Invoke-RemoteBuild] Running dotnet restore..."
-        $restoreResult = Invoke-Command -Session $session -ScriptBlock {
+        $restoreExit = Invoke-Command -Session $session -ScriptBlock {
             param($workDir)
             Set-Location $workDir
-            $output = dotnet restore 2>&1
-            return @{ ExitCode = $LASTEXITCODE; Output = ($output -join "`n") }
+            dotnet restore 2>&1 | ForEach-Object { Write-Host $_ }
+            return $LASTEXITCODE
         } -ArgumentList $GuestWorkDir
 
-        Write-Host $restoreResult.Output
-        if ($restoreResult.ExitCode -ne 0) {
-            throw "dotnet restore failed (exit $($restoreResult.ExitCode))"
+        if ($restoreExit -ne 0) {
+            throw "dotnet restore failed (exit $restoreExit)"
         }
 
         Write-Host "[Invoke-RemoteBuild] Running dotnet build (configuration: $Configuration)..."
-        $buildResult = Invoke-Command -Session $session -ScriptBlock {
+        $buildExit = Invoke-Command -Session $session -ScriptBlock {
             param($workDir, $config, $artifactZip)
             Set-Location $workDir
             $outputDir = Join-Path $workDir 'bin\CIOutput'
-            $output = dotnet build --configuration $config --output $outputDir 2>&1
-            $buildExit = $LASTEXITCODE
+            dotnet build --configuration $config --output $outputDir 2>&1 | ForEach-Object { Write-Host $_ }
+            $exit = $LASTEXITCODE
 
-            if ($buildExit -eq 0) {
+            if ($exit -eq 0) {
                 $archiveDir = Split-Path $artifactZip -Parent
                 if (-not (Test-Path $archiveDir)) {
                     New-Item -ItemType Directory -Path $archiveDir -Force | Out-Null
@@ -186,12 +187,11 @@ try {
                 Compress-Archive -Path "$outputDir\*" -DestinationPath $artifactZip -Force
             }
 
-            return @{ ExitCode = $buildExit; Output = ($output -join "`n") }
+            return $exit
         } -ArgumentList $GuestWorkDir, $Configuration, $GuestArtifactZip
 
-        Write-Host $buildResult.Output
-        if ($buildResult.ExitCode -ne 0) {
-            throw "dotnet build failed (exit $($buildResult.ExitCode))"
+        if ($buildExit -ne 0) {
+            throw "dotnet build failed (exit $buildExit)"
         }
     }