add basic agents.md

Author: reteps

AGENTS.md

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+# Project Overview
+
+This is the PrairieLearn marketing website built with Next.js 16 and TypeScript. It showcases PrairieLearn's educational assessment platform features and hosts content from the PrairieLearn example course via a git submodule.
+
+## Guidelines
+
+- NEVER amend commits or force push unless specifically requested.
+- NEVER rebase unless specifically requested, always use merge commits.
+- NEVER use `as any` casts in TypeScript code to avoid type errors.
+- Don't add extra defensive checks or try/catch blocks that are abnormal for that area of the codebase (especially if called by trusted / validated codepaths).
+- Don't add extra comments that a human wouldn't add or that are inconsistent with the rest of the file.
+
+## Commands
+
+```bash
+yarn dev          # Start development server on localhost:3000
+yarn build        # Production build
+yarn lint         # Run ESLint and Prettier checks
+yarn format       # Auto-format with Prettier
+```
+
+## Git Submodule
+
+The `PrairieLearn/` directory is a git submodule containing the example course content:
+
+```bash
+git submodule init && git submodule update    # Initial setup
+git submodule update --remote                  # Update to latest
+```
+
+## Architecture
+
+### Content Pipeline
+
+The site pulls content from `PrairieLearn/exampleCourse/` and processes it for display:
+
+- **src/lib/catalog/** - Utilities that read markdown files from the submodule, parse frontmatter with `gray-matter`, and expose content for pages
+- **src/remarkPlugins/** - Custom Remark plugins for markdown processing (extractImages, loadCode, rewriteAssessmentLinks)
+- `COURSE_ROOT` in `src/lib/catalog/util.ts` points to `PrairieLearn/exampleCourse/`
+
+### MDX Configuration
+
+MDX support is configured in `next.config.ts` with:
+- Math rendering via `remark-math` and `rehype-katex`
+- GitHub Flavored Markdown via `remark-gfm`
+- Auto-linking headings via `rehype-slug` and `rehype-autolink-headings`
+
+### Page Structure
+
+- **src/pages/** - Next.js page routes (catalog/, about/, products/, pricing/, etc.)
+- **src/components/** - Reusable React components with co-located `.module.scss` files
+- **src/lib/images/** - Static image assets
+
+### Key Components
+
+- `ExampleQuestion.tsx` - Renders interactive PrairieLearn question examples
+- `ExampleEditor.tsx` - Shows code editor examples
+- `BlogMarkdownLayout.tsx` - Layout wrapper for markdown content pages