chore(dev): add VS Code dev container configuration

.devcontainer/README.md

@@ -0,0 +1,92 @@
+# Dev Container Setup
+
+This directory contains the VS Code dev container configuration for OpenSpec development.
+
+## What's Included
+
+- **Node.js 20 LTS** (>=20.19.0) - TypeScript/JavaScript runtime
+- **pnpm** - Fast, disk space efficient package manager
+- **Git + GitHub CLI** - Version control tools
+- **VS Code Extensions**:
+  - ESLint & Prettier for code quality
+  - Vitest Explorer for running tests
+  - GitLens for enhanced git integration
+  - Error Lens for inline error highlighting
+  - Code Spell Checker
+  - Path IntelliSense
+
+## How to Use
+
+### First Time Setup
+
+1. **Install Prerequisites** (on your local machine):
+   - [VS Code](https://code.visualstudio.com/)
+   - [Docker Desktop](https://www.docker.com/products/docker-desktop)
+   - [Dev Containers extension](https://marketplace.visualstudio.com/items?itemName=ms-vscode-remote.remote-containers)
+
+2. **Open in Container**:
+   - Open this project in VS Code
+   - You'll see a notification: "Folder contains a Dev Container configuration file"
+   - Click "Reopen in Container"
+
+   OR
+
+   - Open Command Palette (`Cmd/Ctrl+Shift+P`)
+   - Type "Dev Containers: Reopen in Container"
+   - Press Enter
+
+3. **Wait for Setup**:
+   - The container will build (first time takes a few minutes)
+   - `pnpm install` runs automatically via `postCreateCommand`
+   - All extensions install automatically
+
+### Daily Development
+
+Once set up, the container preserves your development environment:
+
+```bash
+# Run development build
+pnpm run dev
+
+# Run CLI in development
+pnpm run dev:cli
+
+# Run tests
+pnpm test
+
+# Run tests in watch mode
+pnpm test:watch
+
+# Build the project
+pnpm run build
+```
+
+### SSH Keys
+
+Your SSH keys are mounted read-only from `~/.ssh`, so git operations work seamlessly with GitHub/GitLab.
+
+### Rebuilding the Container
+
+If you modify `.devcontainer/devcontainer.json`:
+- Command Palette → "Dev Containers: Rebuild Container"
+
+## Benefits
+
+- No need to install Node.js or pnpm on your local machine
+- Consistent development environment across team members
+- Isolated from other Node.js projects on your machine
+- All dependencies and tools containerized
+- Easy onboarding for new developers
+
+## Troubleshooting
+
+**Container won't build:**
+- Ensure Docker Desktop is running
+- Check Docker has enough memory allocated (recommend 4GB+)
+
+**Extensions not appearing:**
+- Rebuild the container: "Dev Containers: Rebuild Container"
+
+**Permission issues:**
+- The container runs as the `node` user (non-root)
+- Files created in the container are owned by this user

.devcontainer/devcontainer.json

@@ -0,0 +1,68 @@
+{
+  "name": "OpenSpec Development",
+  "image": "mcr.microsoft.com/devcontainers/typescript-node:1-20-bookworm",
+
+  // Additional tools and features
+  "features": {
+    "ghcr.io/devcontainers/features/git:1": {
+      "version": "latest",
+      "ppa": true
+    },
+    "ghcr.io/devcontainers/features/github-cli:1": {
+      "version": "latest"
+    }
+  },
+
+  // Configure tool-specific properties
+  "customizations": {
+    "vscode": {
+      // Set default container specific settings
+      "settings": {
+        "typescript.tsdk": "node_modules/typescript/lib",
+        "typescript.enablePromptUseWorkspaceTsdk": true,
+        "editor.formatOnSave": true,
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
+        "editor.codeActionsOnSave": {
+          "source.fixAll": "explicit"
+        },
+        "files.eol": "\n",
+        "terminal.integrated.defaultProfile.linux": "bash"
+      },
+
+      // Add extensions you want installed when the container is created
+      "extensions": [
+        // TypeScript/JavaScript essentials
+        "dbaeumer.vscode-eslint",
+        "esbenp.prettier-vscode",
+
+        // Testing
+        "vitest.explorer",
+
+        // Git
+        "eamodio.gitlens",
+
+        // Utilities
+        "streetsidesoftware.code-spell-checker",
+        "usernamehw.errorlens",
+        "christian-kohler.path-intellisense"
+      ]
+    }
+  },
+
+  // Use 'forwardPorts' to make a list of ports inside the container available locally
+  // "forwardPorts": [],
+
+  // Use 'postCreateCommand' to run commands after the container is created
+  "postCreateCommand": "corepack enable && corepack prepare pnpm@latest --activate && pnpm install",
+
+  // Configure mounts to preserve SSH keys for git operations
+  "mounts": [
+    "source=${localEnv:HOME}${localEnv:USERPROFILE}/.ssh,target=/home/node/.ssh,readonly,type=bind,consistency=cached"
+  ],
+
+  // Set the default user to 'node' (non-root user)
+  "remoteUser": "node",
+
+  // Ensure git is properly configured
+  "initializeCommand": "echo 'Initializing dev container...'"
+}

.gitignore

@@ -147,3 +147,6 @@ docs/
 .claude/
 CLAUDE.md
 .DS_Store
+
+# Pnpm
+.pnpm-store/