chore: add devcontainer support to ease developer workstation setup

[tinesoft]

Fixes #466

[Copilot]

Pull Request Overview

This PR adds development container (devcontainer) support to simplify developer workstation setup by providing a pre-configured development environment with all necessary tools and AI agents.

• Adds comprehensive devcontainer configuration with Python, .NET, Node.js, and Git
• Creates automated setup script for CLI-based AI agents and development tools
• Updates documentation to guide developers on using the new devcontainer setup

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
CONTRIBUTING.md	Adds documentation section explaining how to use devcontainers with VSCode and GitHub Codespaces
AGENTS.md	Documents how to update devcontainer files when adding new AI agents
.devcontainer/post-create.sh	Automated setup script that installs CLI tools and AI agents
.devcontainer/devcontainer.json	Main devcontainer configuration with base image, features, and VSCode extensions

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[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull Request Overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

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