Fix 'context has already been set' multiprocessing error

Neutralize mp.set_start_method() calls from Applio/torch by using
force=True and catching RuntimeError.

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

pipeline/training.py

@@ -31,6 +31,19 @@ from pipeline.setup import APPLIO_DIR
 
 LOGS_DIR = os.path.join(APPLIO_DIR, "logs")
 
+# Prevent "context has already been set" errors from Applio/torch
+# by neutralizing mp.set_start_method calls
+import multiprocessing as _mp
+_orig_set_start_method = _mp.set_start_method
+
+def _safe_set_start_method(method=None, force=False):
+    try:
+        _orig_set_start_method(method, force=True)
+    except RuntimeError:
+        pass
+
+_mp.set_start_method = _safe_set_start_method
+
 
 def _setup_applio_env():
     """Ensure Applio is on sys.path."""