[ENHANCEMENT] Add Nix support for reproducible builds and dev environment

[randomizedcoder]

Problem (one or two sentences)

Setting up a development environment for Roo Code requires manually installing the correct versions of Node.js, pnpm, and various native build dependencies (Python, pkg-config, OpenSSL, etc.). This leads to:

• "Works on my machine" issues: Different contributors have different tool versions, causing inconsistent builds and hard-to-reproduce bugs

• Onboarding friction: New contributors spend significant time setting up their environment before writing any code

• CI/CD complexity: CI pipelines need to manually orchestrate tool installation

• Native dependency headaches: @vscode/ripgrep and Puppeteer require system-level dependencies that vary by OS

Context (who is affected and when)

Who is affected:

• New contributors setting up their development environment for the first time
• Existing contributors switching machines or reinstalling their OS
• Contributors on NixOS or using Nix as their package manager
• CI/CD systems building and testing the project
• Maintainers debugging issues that may be environment-specific

When it occurs:

• During initial project setup when installing Node.js, pnpm, and native dependencies
• When dependencies change (e.g., Node.js version bump, new native module added)
• When troubleshooting build failures caused by mismatched tool versions
• When onboarding team members or community contributors

Desired behavior (conceptual, not technical)

A contributor should be able to clone the repository and immediately have a fully working development environment with a single command, regardless of their operating system or what tools they have installed globally.
The environment should:

• Provide all required tools at the correct versions
• Handle platform-specific native dependencies automatically
• Be identical for every contributor, eliminating "works on my machine" issues
• Not require manual installation steps or reading lengthy setup documentation
• Support building, testing, and packaging the extension without additional configuration

Constraints / preferences (optional)

• Non-intrusive: Should not affect contributors who don't use Nix - existing workflow (pnpm install && pnpm build) must continue to work unchanged
• Minimal footprint: Only add flake.nix and flake.lock to the repository; avoid Nix-specific configuration scattered across multiple files
• Self-documenting: Include clear usage instructions in the flake header comment and README
• Maintainable: Provide a simple way to update dependency hashes when pnpm-lock.yaml changes
• Platform support: Should work on the same platforms the project already supports (Linux x86_64/aarch64, macOS Intel/Apple Silicon)
• Aligned with nixpkgs: Follow patterns used by the existing vscode-extensions.rooveterinaryinc.roo-cline package in nixpkgs where applicable

Request checklist

• I've searched existing Issues and Discussions for duplicates
• This describes a specific problem with clear context and impact

Roo Code Task Links (optional)

No response

Acceptance criteria (optional)

No response

Proposed approach (optional)

No response

Trade-offs / risks (optional)

No response

[roomote]

I have analyzed this issue and here is my proposed implementation plan:

Proposed Implementation

1. Add flake.nix (root directory)

Create a Nix flake that provides a development shell with:

• Node.js 20 (matching the v20.19.2 in .nvmrc)
• pnpm package manager
• Native build dependencies: pkg-config, openssl, python3, libsecret, and other libraries needed for native modules
• Chromium-related dependencies for puppeteer-chromium-resolver
• Platform support: Linux x86_64/aarch64 and macOS Intel/Apple Silicon (darwin-x86_64/darwin-aarch64)

The flake will expose:

• devShells.default - Full development environment
• Self-documenting header comment with usage instructions

2. Add flake.lock (auto-generated)

This will be automatically created when the flake is first built, pinning nixpkgs to a specific revision for reproducibility.

3. Update .gitignore

Add .direnv entry for contributors using direnv with Nix.

4. Update CONTRIBUTING.md

Add an optional "Using Nix" section explaining:

• How to enter the development environment (nix develop)
• Integration with direnv (optional)
• Benefits of using Nix for development

Key Design Decisions

1. Non-intrusive: The flake is completely optional - existing workflow (pnpm install && pnpm build) remains unchanged
2. Minimal footprint: Only flake.nix and flake.lock are added, with a small documentation update
3. Single command setup: Contributors can clone and run nix develop to get a fully working environment
4. Cross-platform: Supports the same platforms the project already targets

Usage Example

# Clone the repository
git clone https://github.com/RooCodeInc/Roo-Code.git
cd Roo-Code

# Enter development environment (all tools available)
nix develop

# Standard workflow works immediately
pnpm install
pnpm build

Or with direnv:

echo "use flake" > .envrc
direnv allow
# Environment automatically activates when entering the directory

Please mention @roomote in a comment saying that you approve this plan, and I will proceed with the implementation.

[randomizedcoder]

Pull request created
#10811

Demo video
https://youtu.be/izhaXYkqT_4