feat: add expressive offline Russian book TTS

tools/tts/run_piper_training_windows.ps1

@@ -15,6 +15,13 @@ if (Test-Path -LiteralPath $exitPath) {
 
 $exitCode = 1
 try {
+    $latestCheckpoint = Get-ChildItem -LiteralPath (Join-Path $runDir 'checkpoints') `
+        -Filter '*.ckpt' `
+        -File `
+        -Recurse `
+        -ErrorAction SilentlyContinue |
+        Sort-Object LastWriteTimeUtc -Descending |
+        Select-Object -First 1
     $arguments = @(
         '-NoProfile', '-NonInteractive', '-ExecutionPolicy', 'Bypass',
         '-File', (Join-Path $root 'train_piper_windows.ps1'),
@@ -24,6 +31,9 @@ try {
         '-PythonExe', (Join-Path $root '.venv\Scripts\python.exe'),
         '-BatchSize', '16', '-NumWorkers', '0', '-MaxEpochs', '2000'
     )
+    if ($latestCheckpoint) {
+        $arguments += @('-CheckpointPath', $latestCheckpoint.FullName)
+    }
     $process = Start-Process -FilePath 'powershell.exe' `
         -ArgumentList $arguments `
         -RedirectStandardOutput $stdoutPath `