add Dev Container configuration for reproducible development environment

[Princess0407]

Description

Setting up a local urunc development environment requires manually installing Docker, QEMU, Firecracker, Solo5, Cloud-Hypervisor, containerd, CNI plugins, and the Go toolchain. This is documented in the installation guide, but there is no reproducible, one-click environment for new contributors or LFX mentees.

Proposed Work

1. Add .devcontainer/devcontainer.json with:

   • Docker-in-Docker support
   • KVM access for QEMU/Firecracker
   • Pre-installed tools: QEMU, Firecracker, Solo5, Cloud-Hypervisor, containerd, CNI, Go

2. Add .devcontainer/Dockerfile based on Ubuntu 22.04 with all build and runtime dependencies.

3. Configure for GitHub Codespaces compatibility.

4. Document usage in docs/developer-guide/development.md.

Why This Matters

• Lowers the barrier for new contributors who want to run make unittest or make e2etest without host-level VMM installation.
• Provides a consistent environment that matches CI runners (Ubuntu 22.04, specific tool versions).
• Helps LFX mentees and new community members get productive in minutes instead of hours.

Acceptance Criteria

• make unittest passes inside the dev container without additional setup.
• make e2etest can run test_ctr successfully inside the container.
• Documentation explains how to open the project in VS Code Dev Containers or GitHub Codespaces.

Non-Goals

• Replacing the existing installation guide.
• Adding new hypervisor or unikernel support.

I can open a PR if agreed on.

[KHARSHAVARDHAN-eng]

@Princess0407 , i have go through the issue details. can i work on this one... if it is free, u can assign me!!!!

Thanks!!!!

[cmainas]

Hello @Princess0407 ,

do you know if devcontainers allow the use of KVM?

[Princess0407]

Hii @cmainas,

yeahhh... for local VS Code + Docker, we can pass the host's /dev/kvm into the container via devcontainer.json using "runArgs": ["--device=/dev/kvm"]. This allows running QEMU/Firecracker inside the container for full e2e tests. However, GitHub Codespaces standard instances do not support hardware accelerated nested virtualization (KVM), so Firecracker/QEMU-based e2e tests won't run there. The dev container would still be valuable in Codespaces for make unittest, make lint, and build workflows while VM spawning e2e tests would require the local VS Code + Docker path. I can prototype this as a draft PR....should I start with the Dockerfile and devcontainer.json, or would you prefer a different approach?