한국어 코스 구조 및 노트북 링크 수정 (Fix Korean course structure and notebook links)

[Copilot]

This PR fixes several structural and linking issues in the Korean translation of the Hugging Face Course that were affecting the user experience for Korean learners.

Issues Fixed

1. Duplicate Chapter Titles in Table of Contents

The Korean _toctree.yml file contained duplicate entries for "3. 🤗 사전훈련된 모델 미세조정" (Fine-tuning a pretrained model), which caused navigation confusion:

Before:

- title: 3. 🤗 사전훈련된 모델 미세조정
  sections:
  - local: chapter3/2
    title: 데이터 처리
  - local: chapter3/5
    title: 학습 곡선 이해하기

- title: 3. 🤗 사전훈련된 모델 미세조정  # Duplicate!
  sections:
  - local: chapter3/3
    title: Trainer API를 사용한 모델 미세조정

After:

- title: 3. 🤗 사전훈련된 모델 미세조정
  sections:
  - local: chapter3/2
    title: 데이터 처리
  - local: chapter3/3
    title: Trainer API를 사용한 모델 미세조정
  - local: chapter3/5
    title: 학습 곡선 이해하기

2. Incorrect Notebook Links

All Korean course files were linking to English notebooks (course/en/chapter*) instead of Korean ones (course/ko/chapter*), preventing Korean users from accessing localized notebook content.

Before:

notebooks={[
  {label: "Google Colab", value: "https://colab.research.google.com/github/huggingface/notebooks/blob/master/course/en/chapter3/section2.ipynb"},
  {label: "Aws Studio", value: "https://studiolab.sagemaker.aws/import/github/huggingface/notebooks/blob/master/course/en/chapter3/section2.ipynb"},
]}

After:

notebooks={[
  {label: "Google Colab", value: "https://colab.research.google.com/github/huggingface/notebooks/blob/master/course/ko/chapter3/section2.ipynb"},
  {label: "Aws Studio", value: "https://studiolab.sagemaker.aws/import/github/huggingface/notebooks/blob/master/course/ko/chapter3/section2.ipynb"},
]}

Files Changed

• chapters/ko/_toctree.yml: Fixed duplicate chapter structure
• 14 Korean MDX files across chapters 2, 3, 5, and 8: Updated notebook links from English (en) to Korean (ko)

Validation

• ✅ All files referenced in table of contents exist
• ✅ YAML syntax is valid
• ✅ Code formatting standards maintained
• ✅ No broken internal links

This improvement ensures Korean learners have a consistent and properly structured learning experience with access to the correct language-specific resources.

Original prompt

이제 PR을 올릴 거야 title과 Description을 추가해줘

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[braintrue]

Noted.