Update hooks and ignore markdown files in size check

AGENTS.md

@@ -120,6 +120,8 @@ src/
     └── utils.ts                  # General utilities (cn function)
 ```
 
+*Note: A complete, up-to-date project tree is automatically generated on each commit and saved to `docs/project-structure.txt`. This file is generated by the pre-commit hook using `.husky/scripts/generate-project-tree.js` and respects `.gitignore` rules.*
+
 ## Key Systems
 
 ### 0. Task 2 Completion Summary
@@ -304,6 +306,27 @@ damage *= effects.myNewStatMultiplier;
 3. **Add research skill in `constants.ts`**
 4. **Map research to effect in `EFFECT_RESEARCH_MAPPING`**
 
+## Git Hooks (Husky)
+
+This project uses **Husky** to manage git hooks for automated checks and agent assistance:
+
+### Pre-Commit Hook (`.husky/pre-commit`)
+Runs automatically before each commit:
+1. **File Size Check**: Ensures no staged file exceeds 400 lines (improves AI agent readability)
+2. **Project Structure Generation**: Updates `docs/project-structure.txt` with current tree (respects `.gitignore`)
+
+### Post-Merge Hook (`.husky/post-merge`)
+Runs after merging branches:
+- Checks if `package.json` or `package-lock.json` changed
+- Automatically runs `npm install` to sync dependencies
+
+### Implementation Files
+- Hook scripts: `.husky/` directory
+- File size check: `.husky/scripts/check-file-size.js`
+- Tree generator: `.husky/scripts/generate-project-tree.js`
+
+---
+
 ## Common Pitfalls
 
 1. **Forgetting to call `getUnifiedEffects()`**: Always use unified effects for stat calculations
@@ -402,6 +425,9 @@ const useGameStore = create<GameStore>()(
 - **After Task 2**: `page.tsx` reduced from ~2554 to ~548 lines (78% reduction)
 - **After Task 2**: `store.ts` increased due to crafting-slice integration, but better organized
 
+### Automated File Size Check
+A pre-commit hook automatically checks all staged files. Files exceeding **400 lines** will be rejected. The hook runs via Husky and uses `.husky/scripts/check-file-size.js`. If your file is too large, refactor it into smaller modules before committing.
+
 ---
 
 ## 🚫 BANNED CONTENT - NEVER ADD THESE