Add Azure Dev Container configuration with GNU utilities

[Copilot]

Adds Dev Container configuration to standardize development environment with Azure CLI, PowerShell, and GNU toolchain pre-configured.

Changes

• .devcontainer/devcontainer.json: TypeScript/Node.js 20 container with Azure CLI, PowerShell, GitHub CLI, and common-utils features. Mounts ~/.azure for credential persistence.

• .devcontainer/dev.sh: Bash helper script providing build, test, dev, setup, validate, and check commands with environment validation and colored output.

• .devcontainer/README.md: Setup documentation for VS Code and GitHub Codespaces with troubleshooting guidance.

• README.md: Added Development section linking to dev container docs.

Configuration Highlights

{
  "features": {
    "ghcr.io/devcontainers/features/azure-cli:1": {"version": "latest"},
    "ghcr.io/devcontainers/features/powershell:1": {"version": "latest"},
    "ghcr.io/devcontainers/features/common-utils:2": {
      "installZsh": true,
      "upgradePackages": true
    }
  },
  "postCreateCommand": "npm install && chmod +x .devcontainer/dev.sh"
}

Helper script usage:

.devcontainer/dev.sh dev      # build + test
.devcontainer/dev.sh validate # check Azure login status

Original prompt

Reference: 8d2dc99

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[github-actions]

This PR is idle because it has been open for 14 days with no activity.

[github-actions]

This PR is idle because it has been open for 14 days with no activity.