Add copilot instructions and linter workflow

.github/instructions/git.instructions.md

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+# GitHub Copilot Instructions
+
+## Git Commit Guidelines
+
+### Commit Message Format
+
+- Use imperative mood in commit messages (e.g., "Add feature" not "Added feature")
+- Start with a verb: Add, Update, Fix, Remove, Refactor, etc.
+- Keep the summary line under 50 characters
+- Use present tense
+
+### Commit Message Structure
+
+```plaintext
+<type>: <short summary>
+
+<detailed description (optional)>
+```
+
+### Types
+
+- `feat`: New feature or content
+- `fix`: Bug fix or correction
+- `docs`: Documentation changes
+- `style`: Formatting, CSS changes (no code change)
+- `refactor`: Code refactoring
+- `chore`: Maintenance tasks
+
+### Examples
+
+Good commit messages:
+
+- `feat: Add atomic habits book review post`
+- `fix: Correct typo in classification metrics post`
+- `style: Update post layout spacing`
+- `docs: Update README with setup instructions`
+
+### Description Guidelines
+
+- Explain WHAT changed and WHY (not HOW)
+- Use bullet points for multiple changes
+- Reference issue numbers if applicable
+- Keep it concise but informative

.github/instructions/markdown.instructions.md

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+---
+applyTo: "**/*.md"
+---
+
+# Markdown Files Instructions
+
+## Post Files
+
+- All blog posts must be placed in `_posts/` directory
+- Use filename format: `YYYY-MM-DD-title.md` (e.g., `2025-12-13-my-post.md`)
+- Always include YAML front matter at the top of each post
+
+## YAML Front Matter
+
+Required fields:
+
+- `layout: post`
+- `title: "Your Post Title"`
+
+Optional but recommended:
+
+- `subtitle: "A brief description"`
+- `tags: [tag1, tag2, tag3]`
+- `comments: true/false`
+
+## Content Structure
+
+- Use clear heading hierarchy (h2, h3, h4)
+- Add blank lines between sections for readability
+- Use code blocks with language specification (e.g., ```python,```javascript)
+- Include alt text for all images
+
+## Writing Style
+
+- Write content in English
+- Keep paragraphs concise and focused
+- Use lists for better readability
+- Add relevant tags for post categorization

.github/workflows/markdown-lint.yml

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+name: Markdown Lint
+
+on:
+  pull_request:
+    paths:
+      - "**.md"
+  workflow_dispatch:
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Markdown Lint
+        uses: DavidAnson/markdownlint-cli2-action@v16
+        with:
+          globs: |
+            **/*.md
+            !node_modules

.markdownlint.json

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+{
+  "default": true,
+  "MD003": {
+    "style": "atx"
+  },
+  "MD007": {
+    "indent": 2
+  },
+  "MD013": {
+    "line_length": 1000,
+    "code_blocks": false,
+    "tables": false
+  },
+  "MD024": {
+    "siblings_only": true
+  },
+  "MD033": false,
+  "MD041": false
+}