Fix F821: Add missing scenario_name definition

- scenario_name was used at line 494 but never defined
- Added: scenario_name = args.test.stem (line 472)
- This fixes the PEP8 F821 error in PR 375
- Matches master branch implementation

Author: ayefimov-1

roles/telemetry_chargeback/files/gen_synth_loki_data.py

@@ -468,6 +468,10 @@ def main():
         logger.critical(f"Failed to load config: {e}")
         return
 
+    # Derive scenario name from test file path
+    scenario_name = args.test.stem
+    logger.info(f"Derived scenario name from test file: {scenario_name}")
+
     # Get generation parameters from config
     generation_config = config.get("generation", {})
     days = generation_config.get("days", 30)