dev: add AGENTS.md

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 CONTRIBUTING.md
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+AGENTS.md

AGENTS.md

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+# Agent Workflow
+
+## Project Overview
+
+Visualizer is a WordPress plugin for creating interactive charts and tables. It uses Google Visualization API, Chart.js, and DataTables.net as rendering libraries. Charts are stored as a custom post type (`visualizer`) with post meta prefixed `visualizer-*`. The plugin has both a classic PHP/jQuery dashboard editor and a React-based Gutenberg block editor — changes to chart settings UI must be synchronized in both.
+
+## Commands
+
+### PHP
+```bash
+composer install                    # Install PHP dependencies
+composer lint                       # Run PHPCS (WordPress coding standards)
+composer format                     # Auto-fix PHPCS issues
+composer phpstan                    # Run PHPStan static analysis (level 6)
+./vendor/bin/phpunit                # Run all PHPUnit tests
+./vendor/bin/phpunit tests/test-export.php  # Run a single test file
+```
+
+### Gutenberg Block (from `classes/Visualizer/Gutenberg/`)
+```bash
+npm install                         # Install JS dependencies
+npm run build                       # Production build
+npm run dev                         # Watch mode for development
+```
+
+### E2E Tests & Environment
+```bash
+npm install                         # Install root JS dependencies (Playwright, etc.)
+npm run test:env:start              # Start wp-env WordPress environment
+npm run test:env:stop               # Stop wp-env
+npm run test:e2e:playwright         # Run Playwright E2E tests
+npm run test:e2e:playwright:debug   # Run Playwright tests with UI
+```
+
+## Architecture
+
+### Module System
+The plugin uses a module-based architecture rooted in `classes/Visualizer/`. Each module extends `Visualizer_Module`:
+
+- **Module/Admin** — Admin dashboard, chart library page
+- **Module/Frontend** — Frontend rendering, shortcode handling, asset enqueueing
+- **Module/Chart** — Chart CRUD operations
+- **Module/Sources** — Data source management
+- **Module/Wizard** — First-time setup wizard
+- **Module/AMP** — AMP compatibility
+
+### Data Flow
+1. Chart markup is placed on page via shortcode (`[visualizer id="123"]`) or Gutenberg block (`gutenberg_block_callback` in `Block.php`)
+2. Chart data is loaded into `window.visualizer` global object (also available via REST endpoint)
+3. `js/render-facade.js` scans for chart markup and dispatches rendering to the appropriate library
+4. Library-specific renderers: `js/render-google.js`, `js/render-chartjs.js`, `js/render-datatables.js`
+
+### Two Editor Systems
+- **Classic editor**: PHP templates in `classes/Visualizer/Render/` with jQuery interactions in `js/frame.js` and `js/library.js`
+- **Gutenberg block**: React components in `classes/Visualizer/Gutenberg/src/`, built with Webpack to `classes/Visualizer/Gutenberg/build/`
+
+Import UI lives in `classes/Visualizer/Render/Layout.php` (classic) and `classes/Visualizer/Gutenberg/src/Components/Import` (Gutenberg).
+
+### Data Sources
+Source handlers in `classes/Visualizer/Source/` parse CSV, JSON, database queries, and post meta. Sample data files are in `samples/`.
+
+### Pro Version
+The plugin checks for a companion `visualizer-pro` plugin. Pro features (database import, WooCommerce reports, advanced chart types) are in the separate `visualizer-pro` repository at `inc/addon.php`.
+
+## Key Configuration
+- **Plugin constants and post type**: `classes/Visualizer/Plugin.php`
+- **Plugin entry point and autoloader**: `index.php`
+- **PHPCS rules**: `phpcs.xml` (WordPress-Core + WordPress-Docs)
+- **PHPStan**: `phpstan.neon` (level 6, baseline in `phpstan-baseline.neon`)
+- **Playwright config**: `tests/e2e/playwright.config.js`
+- **Semantic release**: `.releaserc.yml`
+
+## Coding Standards
+- Follow WordPress Coding Standards (enforced by PHPCS)
+- PHP 7.4 minimum compatibility
+- Text domain: `visualizer`
+- Escape all output (`esc_html()`, `esc_attr()`, `wp_kses_post()`)
+- Sanitize all input (`sanitize_text_field()`, etc.)
+- Prepare all database queries with `$wpdb->prepare()`
+- Use WordPress nonces for form submissions