chore: import upstream snapshot with attribution

.devcontainer/README.md

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+# Sim Development Container
+
+Development container configuration for VS Code Dev Containers and GitHub Codespaces.
+
+## Prerequisites
+
+- Visual Studio Code
+- Docker Desktop or Podman Desktop
+- VS Code Dev Containers extension
+
+## Getting Started
+
+1. Open this project in VS Code
+2. Click "Reopen in Container" when prompted (or press `F1` → "Dev Containers: Reopen in Container")
+3. Wait for the container to build and initialize
+4. Start developing with `sim-start`
+
+The setup script will automatically install dependencies and run migrations.
+
+## Development Commands
+
+### Running Services
+
+You have two options for running the development environment:
+
+**Option 1: Run everything together (recommended for most development)**
+```bash
+sim-start  # Runs both app and socket server using concurrently
+```
+
+**Option 2: Run services separately (useful for debugging individual services)**
+- In the **app** container terminal: `sim-app` (starts Next.js app on port 3000)
+- In the **realtime** container terminal: `sim-sockets` (starts socket server on port 3002)
+
+### Other Commands
+
+- `sim-migrate` - Push schema changes to the database
+- `sim-generate` - Generate new migrations
+- `build` - Build the application
+- `pgc` - Connect to PostgreSQL database
+
+## Troubleshooting
+
+**Build errors**: Rebuild the container with `F1` → "Dev Containers: Rebuild Container"
+
+**Port conflicts**: Ensure ports 3000, 3002, and 5432 are available
+
+**Container runtime issues**: Verify Docker Desktop or Podman Desktop is running
+
+## Technical Details
+
+Services:
+- **App container** (8GB memory limit) - Main Next.js application
+- **Realtime container** (4GB memory limit) - Socket.io server for real-time features
+- **Database** - PostgreSQL with pgvector extension
+- **Migrations** - Runs automatically on container creation
+
+You can develop with services running together or independently.
+
+### Personalization
+
+**Project commands** (`sim-start`, `sim-app`, etc.) are automatically available via `/workspace/.devcontainer/sim-commands.sh`.
+
+**Personal shell customization** (aliases, prompts, etc.) should use VS Code's dotfiles feature:
+1. Create a dotfiles repository (e.g., `github.com/youruser/dotfiles`)
+2. Add your `.bashrc`, `.zshrc`, or other configs
+3. Configure in VS Code Settings:
+   ```json
+   {
+     "dotfiles.repository": "youruser/dotfiles",
+     "dotfiles.installCommand": "install.sh"
+   }
+   ```
+
+This separates project-specific commands from personal preferences, following VS Code best practices.