Remove redundant detect_scenario from LossDebugger

Translate all notebook content from Korean to English

Clear notebook outputs and add real checkpoint diagnosis cell

Add missing mock_history cases for full diagnose_status coverage

Fix debugger reference data and scenario detection logic

Standardize notebooks for Colab/local dual environment support

Use LLaMA 2 pretrained tokenizer and remove tokenizer_mode option

feat(training): add LossDebugger 5-level diagnostic framework