feat: add agent instructions and project structure documentation

Author: SabotageAndi

agent.md

@@ -0,0 +1,113 @@
+# Agent Instructions
+
+This repository contains the Jekyll-based static website for **DotNetDevs.at**, a non-profit Austrian .NET developer community that hosts monthly meetup events.
+
+## Tech Stack
+
+- **Static Site Generator**: Jekyll >= 3.7 with Minimal Mistakes theme
+- **Ruby**: Managed via Gemfile (github-pages gem)
+- **Node.js**: For testing only
+- **Testing**: Playwright (approval/visual snapshot testing)
+- **Hosting**: GitHub Pages
+
+## Prerequisites
+
+```bash
+bundle install   # Install Ruby gems
+npm install      # Install Node.js dependencies
+```
+
+## Development Commands
+
+| Command | Purpose |
+|---------|---------|
+| `npm run serve` | Start local dev server at http://127.0.0.1:4000 |
+| `npm run build` | Build the Jekyll site |
+| `npm test` | Run Playwright tests |
+| `npm run test:update-snapshots` | Update visual/approval snapshots |
+| `npm run test:ui` | Run tests with Playwright UI |
+
+## Content Structure
+
+### Events (`_events/`)
+
+Filename pattern: `YYYY-MM-DD.md` or `YYYY-MM-DD-talkN.md` for multiple talks on the same day.
+
+Required front matter:
+
+```yaml
+---
+date: 2025-01-14
+title: "Event Title"
+speakers:
+  - Speaker Name
+Location: "Rubicon"
+InPersonLink: "https://meetup.com/..."
+RemoteLink: "https://meetup.com/..."
+RecordingLink: ""  # YouTube URL after event, empty string before
+Registrations: 0
+Participants: 0
+Viewers: 0
+public: true  # Set to false to hide from listing
+abstract: |
+    Talk description...
+---
+```
+
+### Speakers (`_speakers/`)
+
+Filename: `firstname-lastname.md` (kebab-case)
+
+```yaml
+---
+name: Full Name
+---
+```
+
+### Sponsors (`_sponsors/`)
+
+```yaml
+---
+title: Sponsor Name
+permalink: /sponsors/sponsor-slug/
+logo: /assets/images/sponsor.svg
+---
+```
+
+## Important Rules
+
+1. **Always run tests** with `npm test` before committing changes
+2. **Update snapshots** with `npm run test:update-snapshots` after intentional visual changes
+3. **Event visibility**: Set `public: true` for events to appear on the website
+4. **Speaker name matching**: Speaker names in event files must exactly match the `name` field in speaker files for auto-linking
+5. **Date format**: Use ISO format `YYYY-MM-DD` in filenames and front matter
+6. **Future events**: Are displayed because `future: true` is set in `_config.yml`
+
+## Testing
+
+The project uses approval testing with Playwright:
+
+- **Visual snapshots**: Screenshots compared against baselines
+- **Structure snapshots**: JSON snapshots of page structure
+- **Test files**: Located in `tests/` directory
+
+Run the full test suite before any PR:
+
+```bash
+npm run test:ci  # Builds site and runs tests
+```
+
+## Project Structure
+
+```
+_config.yml      # Jekyll configuration
+_data/           # Navigation and UI text
+_events/         # Event markdown files
+_speakers/       # Speaker profiles
+_sponsors/       # Sponsor information
+_includes/       # Reusable HTML partials
+_layouts/        # Page templates
+_sass/           # SCSS stylesheets
+assets/          # Images, CSS, JS
+tests/           # Playwright test specs
+```