ignore build folder and update documentation

.gitignore

@@ -2,7 +2,7 @@
 node_modules/
 
 # Build output
-#build/
+build/
 
 # Logs
 *.log

AGENTS.md

@@ -23,6 +23,7 @@ This project builds a presentation deck for Marp based on Markdown files.
 - Use `slides/` directory for Markdown slide files
 - Use `assets/` for images and media files
 - Use `themes/` for custom Marp themes
+- Use `build/` directory for generated output files (ignored by git)
 
 ### Naming Conventions
 - Slide files: `index.md`, `additional-slides.md` (descriptive names)

README.md

@@ -48,7 +48,7 @@ Generate HTML files from Markdown:
 ```bash
 npm run build
 ```
-Output files are created in the `build/` directory.
+Output files are created in the `build/` directory (ignored by git).
 
 ### Export Formats
 
@@ -56,13 +56,13 @@ Output files are created in the `build/` directory.
 ```bash
 npm run export:pdf
 ```
-Generates PDF files in the `build/` directory.
+Generates PDF files in the `build/` directory (ignored by git).
 
 #### HTML Export
 ```bash
 npm run export:html
 ```
-Generates standalone HTML files in the `build/` directory.
+Generates standalone HTML files in the `build/` directory (ignored by git).
 
 ### Watch Mode
 
@@ -82,7 +82,7 @@ malta-slides-marp/
 ├── assets/                # Images and media files
 ├── themes/                # Custom CSS themes
 │   └── custom-theme.css   # Example custom theme
-├── build/                 # Generated output files
+├── build/                 # Generated output files (ignored by git)
 ├── node_modules/          # Dependencies
 ├── package.json           # Project configuration
 ├── Makefile               # Alternative build commands