feat(plugin-api): create foundational plugin API package

- Add @super-productivity/plugin-api package with TypeScript definitions
- Define core plugin interfaces, types, and manifest structure
- Add plugin hooks system for event-driven architecture
- Create plugin API type definitions and constants
- Add documentation and development guidelines

packages/plugin-dev/boilerplate-solid-js/README.md

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+# Solid.js Boilerplate Plugin for Super Productivity
+
+A modern, TypeScript-based boilerplate for creating Super Productivity plugins using Solid.js.
+
+## Features
+
+- 🚀 **Solid.js** - Fast, reactive UI framework
+- 📘 **TypeScript** - Full type safety with Super Productivity Plugin API
+- 🎨 **Modern UI** - Clean, responsive design with dark mode support
+- 🔧 **Vite** - Lightning-fast development and build tooling
+- 📦 **Ready to Use** - Complete setup with examples for all plugin features
+
+## Getting Started
+
+### Prerequisites
+
+- Node.js 16+
+- npm or yarn
+- Super Productivity 8.0.0+
+
+### Installation
+
+1. Clone this boilerplate:
+
+```bash
+cd packages/plugin-dev
+cp -r boilerplate-solid-js my-plugin
+cd my-plugin
+```
+
+2. Install dependencies:
+
+```bash
+npm install
+```
+
+3. Update plugin metadata in `src/manifest.json`:
+   - Change `id` to a unique identifier
+   - Update `name`, `description`, and `author`
+   - Modify `permissions` and `hooks` as needed
+
+### Development
+
+Run the development server:
+
+```bash
+npm run dev
+```
+
+This starts Vite in watch mode. Your plugin will rebuild automatically when you make changes.
+
+### Building
+
+Build the plugin for production:
+
+```bash
+npm run build
+```
+
+This creates optimized files in the `dist/` directory.
+
+### Packaging
+
+Create a ZIP file for distribution:
+
+```bash
+npm run package
+```
+
+This will:
+
+1. Build the plugin
+2. Create a ZIP file containing all necessary files
+3. Place the ZIP in the root directory
+
+## Project Structure
+
+```
+src/
+├── assets/          # Static assets (icons, images)
+│   └── icon.svg     # Plugin icon
+├── app/             # Solid.js application
+│   ├── App.tsx      # Main app component
+│   └── App.css      # App styles
+├── index.html       # Plugin UI entry point
+├── index.ts         # UI initialization
+├── plugin.ts        # Plugin logic and API integration
+└── manifest.json    # Plugin metadata
+
+scripts/            # Build and utility scripts
+└── build-plugin.js  # Plugin packaging script
+
+dist/               # Build output (gitignored)
+├── assets/
+├── index.html
+├── index.js
+├── plugin.js
+└── manifest.json
+```
+
+## Plugin API Usage
+
+### Basic Setup
+
+The plugin API is exposed through the global `plugin` object in `plugin.ts`:
+
+```typescript
+import { PluginInterface } from '@super-productivity/plugin-api';
+
+declare const plugin: PluginInterface;
+```
+
+### Common API Methods
+
+#### UI Registration
+
+```typescript
+// Register header button
+plugin.registerHeaderButton({
+  icon: 'rocket',
+  tooltip: 'Open Plugin',
+  action: () => plugin.showIndexHtmlAsView(),
+});
+
+// Register menu entry
+plugin.registerMenuEntry({
+  label: 'My Plugin',
+  icon: 'rocket',
+  action: () => plugin.showIndexHtmlAsView(),
+});
+
+// Register keyboard shortcut
+plugin.registerShortcut({
+  keys: 'ctrl+shift+m',
+  label: 'Open My Plugin',
+  action: () => plugin.showIndexHtmlAsView(),
+});
+```
+
+#### Data Operations
+
+```typescript
+// Get tasks
+const tasks = await plugin.getTasks();
+const archivedTasks = await plugin.getArchivedTasks();
+
+// Create task
+const newTask = await plugin.addTask({
+  title: 'New Task',
+  projectId: 'project-id',
+});
+
+// Update task
+await plugin.updateTask('task-id', {
+  title: 'Updated Title',
+  isDone: true,
+});
+
+// Get projects and tags
+const projects = await plugin.getAllProjects();
+const tags = await plugin.getAllTags();
+```
+
+#### Event Hooks
+
+```typescript
+// Task completion
+plugin.on('taskComplete', (task) => {
+  console.log('Task completed:', task.title);
+});
+
+// Task updates
+plugin.on('taskUpdate', (task) => {
+  console.log('Task updated:', task);
+});
+
+// Context changes
+plugin.on('contextChange', (context) => {
+  console.log('Context changed:', context);
+});
+```
+
+#### Communication with UI
+
+In `plugin.ts`:
+
+```typescript
+plugin.onMessage('myCommand', async (data) => {
+  // Handle message from UI
+  return { result: 'success' };
+});
+```
+
+In your Solid.js component:
+
+```typescript
+const sendMessage = async (type: string, payload?: any) => {
+  return new Promise((resolve) => {
+    const messageId = Math.random().toString(36).substr(2, 9);
+
+    const handler = (event: MessageEvent) => {
+      if (event.data.messageId === messageId) {
+        window.removeEventListener('message', handler);
+        resolve(event.data.response);
+      }
+    };
+
+    window.addEventListener('message', handler);
+    window.parent.postMessage({ type, payload, messageId }, '*');
+  });
+};
+
+// Usage
+const result = await sendMessage('myCommand', { foo: 'bar' });
+```
+
+## Customization
+
+### Styling
+
+The boilerplate includes:
+
+- CSS custom properties for theming
+- Dark mode support
+- Responsive design
+- Minimal, clean styling
+
+Modify `src/app/App.css` to customize the appearance.
+
+### Adding Features
+
+1. **New UI Components**: Add them in `src/app/` as `.tsx` files
+2. **New API Endpoints**: Add handlers in `src/plugin.ts` using `plugin.onMessage()`
+3. **New Hooks**: Register them in `manifest.json` and handle in `plugin.ts`
+4. **Permissions**: Add required permissions to `manifest.json`
+
+## Best Practices
+
+1. **Type Safety**: Always use TypeScript types from `@super-productivity/plugin-api`
+2. **Error Handling**: Wrap async operations in try-catch blocks
+3. **Performance**: Use Solid.js signals and effects efficiently
+4. **Security**: Never expose sensitive data or operations
+5. **User Experience**: Provide loading states and error feedback
+
+## Deployment
+
+1. Build the plugin: `npm run build`
+2. Package it: `npm run package`
+3. Upload the ZIP file to Super Productivity:
+   - Open Super Productivity
+   - Go to Settings → Plugins
+   - Click "Upload Plugin"
+   - Select your ZIP file
+
+## Troubleshooting
+
+### Plugin not loading
+
+- Check browser console for errors
+- Verify `manifest.json` is valid JSON
+- Ensure `minSupVersion` matches your Super Productivity version
+
+### API calls failing
+
+- Check if you have required permissions in `manifest.json`
+- Verify Super Productivity is running the correct version
+- Look for error messages in the console
+
+### Build errors
+
+- Run `npm run typecheck` to check for TypeScript errors
+- Ensure all dependencies are installed
+- Clear `node_modules` and reinstall if needed
+
+## Resources
+
+- [Super Productivity Plugin API Documentation](https://github.com/johannesjo/super-productivity)
+- [Solid.js Documentation](https://www.solidjs.com/docs/latest)
+- [Vite Documentation](https://vitejs.dev/)
+
+## License
+
+This boilerplate is provided as-is for creating Super Productivity plugins. Feel free to modify and distribute your plugins as you see fit.